Zinc
Nutrient Name: Zinc.
Elemental Symbol: Zn.
Forms: Zinc acetate, zinc arginate, zinc ascorbate, zinc aspartate, zinc carbonate, zinc citrate, zinc gluconate, zinc glycerate, zinc glycinate, zinc histidinate, zinc lactate, zinc methionate, zinc monomethionine, zinc oxide, zinc picolinate, zinc selenate, zinc sulfate, zinc undecylenate.
Drug/Class Interaction Type | Mechanism and Significance | Management | Amphetamines Related stimulant medications Methylphenidate
| Zinc may directly benefit patients with ADHD, and coadministration with mixed-amphetamine salts may provide enhanced therapeutic effects. Benefit may be more probable in older and heavier individuals with low zinc and free fatty acid levels, but research indicates children may also benefit. Adverse effects unlikely. Further research warranted.
| Coadminister, when indicated. Complement with low-dose copper with long-term use.
| Androgens
| Zinc is key to normal male sexual function, including testosterone formation, spermatogenesis, and prostate function, as well as ovulation and fertilization in females. Deficiency can cause hypogonadism, and administration can elevate testosterone levels, raise sperm counts, and enhance action of androgen therapy, especially when pretreatment zinc levels are low. Adverse effects unlikely. Further research warranted.
| Consider coadministration for synergistic effect. Complement with low-dose copper with long-term use.
| Antibiotics, oral / /
| Zinc plays central role in immunocompetence and may enhance acute immune response. Combination of oral antibiotics and zinc may benefit some patients, particularly those with compromised zinc status, but may be contraindicated in treatment of pneumonia during hot weather. Further research warranted.
| Coadminister, when indicated, in infants and children, especially with poor zinc nutriture. Routine pediatric prophylaxis may be contraindicated.
| Antibiotics, topical
| In addition to zinc’s general activity in supporting healthy skin and immune function, its bacteriostatic activity against Propionibacterium acnes and its role in polymorphonuclear leukocyte chemotaxis are beneficial in treating inflammatory acne. Coadministration of zinc, topical or oral, with topical antibiotics may enhance treatment of acne vulgaris. Adverse effects unlikely. Further research warranted.
| Consider coadministration of oral zinc for synergistic effect. Complement with low-dose copper with long-term use.
| Antidepressants, tricyclic Antidepressants, selective serotonin reuptake inhibitor (SSRI)
| The central nervous system and hippocampal and cortical neurons, in particular, rely on high concentrations of zinc to modulate the excitatory (glutamatergic) and inhibitory (GABAergic) amino acid neurotransmission pathways. Administration of zinc increases levels of synaptic pool zinc in hippocampus and promotes changes in brain similar to antidepressants. Zinc deficiency may contribute to depression, and coadministration may potentiate activity of antidepressant medications by one or more mechanisms. Further research warranted.
| Consider coadministration of oral zinc for synergistic effect. Complement with low-dose copper with long-term use.
| Captopril, enalapril Angiotensin-converting enzyme (ACE) inhibitors /
| ACE inhibitors possess a prominent zinc-binding moiety that binds to zinc ions. Zinc depletion at tissue levels and possibly deficiency can occur, with effects of captopril being more rapid than those of enalapril. Concomitant zinc can prevent or reverse depletion. Adverse effects unlikely. Further research warranted.
| Watch for clinical signs of zinc depletion; lab tests often unreliable. Coadminister to prevent depletion. Complement with low-dose copper during long-term use.
| Chlorhexidine /
| Coadministration of zinc can enhance binding affinity, reduce severity of chlorhexidine-induced staining, and enhance plaque-inhibiting effect.
| Combining zinc with chlorhexidine indicated for reducing adverse effects and increasing efficacy.
| Ciprofloxacin Fluoroquinolone/quinolone antibiotics / / /
| Binding may occur with simultaneous intake and inhibit absorption and bioavailability of both agents. Decreased therapeutic activity probable with interaction; minimal effect with separation of intake. Limited evidence on long-term effects.
| Avoid zinc, or separate intake during short-term therapy. Separate intake by several hours.
| Clobetasol Corticosteroids, topical
| Coadministration of zinc and clobetasol (and biotin) may enhance therapeutic effect in treatment of inflammatory dermatological conditions.
| Consider coadministration, with biotin, for synergistic effect. Complement with low-dose copper with long-term use.
| Corticosteroids, oral /
| Adenohypophyseal-adrenocortical network helps maintain circulating zinc and mobilize zinc from tissue stores. Internal or exogenous glucocorticoids can affect zinc metabolism. In particular, oral corticosteroids can elevate urinary zinc excretion and lower serum zinc levels. Coadministration of zinc may prevent or reverse depletion, but research is needed to rule out potential interference or adverse effects.
| Coadminister to prevent depletion. Complement with low-dose copper with long-term use. Watch for clinical signs of zinc depletion with extended steroid therapy; lab tests often unreliable.
| Estrogens, conjugated Oral contraceptives (OCs) Medroxyprogesterone Estrogen replacement therapy (ERT) /
| OCs may decrease serum levels of zinc. However, conjugated estrogens and medroxyprogesterone may reduce previously elevated urinary zinc excretion in osteoporotic postmenopausal women. Further research is warranted to determine varying effects of different estrogen compounds in their respective patient populations.
| Women using OCs may have increased needs for zinc based on potential depletion, as well as possibly higher needs for folate and vitamins B12and B6. ERT may enhance zinc status. Individual evaluation of safe and effective hormone dosage levels necessary. END_ | Histamine (H2) receptor antagonists Antacids Gastric acid–suppressive medications
| Agents that interfere with normal acid environment of the stomach can impair zinc absorption and reduce availability; although among H2blockers, cimetidine appears to be an exception. Adverse effects on zinc status may be slow to develop and difficult to assess. Administration of zinc can prevent or reverse depletion and enhance healing of gastric tissue damaged by ulceration.
| Coadministration of zinc can aid in gastric tissue repair and prevent possible depletion. Consider cimetidine. Separate intake by at least 2 hours to avoid compromised gastric pH. Complement with low-dose copper with long-term use.
| Loop diuretics
| Loop diuretics can increase urinary zinc excretion, but probably to a lesser degree than thiazide diuretics. Adverse effects from zinc administration unlikely. Further research warranted.
| Consider concomitant zinc to prevent depletion. Watch for clinical signs of zinc depletion with extended diuretic therapy; lab tests often unreliable. Complement with low-dose copper with long-term use.
| Metronidazole (vaginal)
| Combination of metronidazole and zinc may exert greater therapeutic activity in trichomoniasis than either agent alone. Adverse effects unlikely. Further research warranted.
| Consider coadministration for synergistic effect, especially with recurrent trichomoniasis or compromised immune status.
| Nonsteroidal anti-inflammatory drugs (NSAIDs) / / /
| NSAIDs and other anti-inflammatory agents may increase urinary zinc excretion and contribute to zinc depletion. NSAIDs may complex with zinc (and other metals) and decrease absorption and bioavailability of these substances. Many individuals with inflammatory conditions tend to have low zinc levels. Concomitant administration may provide enhanced therapeutic effects, but intake should be separated. Further research into potential synergy as well as possible nutrient depletion with long-term NSAID use warranted.
| Consider concomitant zinc to prevent depletion and possibly enhance effects. Watch for clinical signs of zinc depletion with extended NSAID therapy; lab tests often unreliable. Separate intake by 2 or more hours. Complement with low-dose copper with long-term use.
| Penicillamine / / / /
| Penicillamine is a chelating agent applied to treat overload and intoxification involving copper, iron, and other metals. Zinc reduces copper levels by inducing intestinal cell metallothionein, which then forms a mucosal block, preventing copper absorption and increasing copper excretion in the stool. Concurrent use of penicillamine and zinc may enhance copper limitation and therapeutic outcomes in treatment of Wilson’s disease. However, oral zinc intake may bind medication doses when ingested concurrently, reducing absorption of both agents. Penicillamine may deplete zinc, even with timing precautions. Further research warranted.
| Consider concomitant zinc to enhance effects for reducing copper levels, with separated intake. Close supervision and monitoring necessary. Supplementation with multiple nutrients may be appropriate with extended therapy if depletion detected; separate intake by several hours.
| Potassium-sparing diuretics / /
| Potassium-sparing diuretics affect zinc in diverse ways. Amiloride may cause zinc accumulation by reducing urinary excretion, whereas triamterene may increase urinary zinc excretion in short term and may cause depletion with extended use. Amiloride is sometimes combined with thiazide diuretic to reduce zinc loss. Further investigation warranted into potential depletion effects with long-term use.
| Consider concomitant zinc to prevent depletion and possibly enhance effects. Monitor for clinical signs of zinc depletion with any long-term diuretic therapy; lab tests often unreliable. Separate intake by 2 or more hours. Complement with low-dose copper with long-term use.
| Radiotherapy
| Preceding or concurrent zinc may prevent or reduce loss or alteration of taste sensation and hasten recovery with radiation therapy to head and neck. Adverse effects unlikely. Further research warranted.
| Consider concomitant zinc to prevent, mitigate, or reverse adverse effects on taste sensation.
| Tetracycline antibiotics / /
| Chelation between zinc and tetracycline-class antibiotics (other than doxycycline) and impaired absorption of both agents, to clinically significant degree, possible with concurrent intake. Zinc intake, even small amounts, could impair antimicrobial activity. General consensus despite minimal direct evidence. Zinc depletion possible with extended tetracycline use, but evidence lacking.
| Discontinue zinc (including zinc-rich foods), or separate intake during short-term therapy. Consider doxycycline. Zinc supplementation may be appropriate with extended therapy, but caution warranted, even with established zinc depletion; separate intake by several hours.
| Thiazide diuretics
| Thiazide diuretics can increase urinary zinc excretion, possibly causing clinically significant deficiency. Coadministration of amiloride may mitigate this adverse effect, whereas concurrent use of ACE inhibitor may exacerbate zinc loss.
| Concomitant zinc may be appropriate if depletion occurs or deficiency develops. Monitor for clinical signs of zinc depletion with any long-term diuretic therapy; lab tests often unreliable. Complement with low-dose copper with long-term use.
| Valproic acid Anticonvulsant medications (AEDs)
| Zinc may play a role in activity of anticonvulsants. Risk of decreased zinc levels is greater with VPA, alone or in combination with other anticonvulsant agents. Further, VPA can alter homeostasis of both zinc and copper and may cause depletion of either or both. Research into protective benefits of zinc coadministration limited, and further investigation warranted.
| Concomitant zinc may be appropriate if depletion occurs or deficiency develops. Monitor for clinical signs of zinc depletion with any long-term AED therapy, especially VPA; lab tests often unreliable. Complement with low-dose copper with long-term use.
| Warfarin Oral vitamin K antagonist anticoagulants / /
| Binding may occur with simultaneous intake and inhibit absorption and bioavailability of both agents. Decreased therapeutic activity probable with interaction; minimal effect with separation of intake. General consensus despite minimal direct evidence. Evidence on long-term effects lacking.
| Concomitant zinc may be appropriate if depletion occurs or deficiency develops. Monitor for clinical signs of zinc depletion with any long-term AED therapy, especially VPA; lab tests often unreliable. Complement with low-dose copper with long-term use.
| Zidovudine (AZT) Nucleoside or nonnucleoside (analog) reverse-transcriptase inhibitors (NRTIs or NNRTIs) / / /
| Zinc is central to numerous immune functions, but AZT may deplete zinc levels. In addition, zinc deficiency may diminish drug effectiveness because zidovudine and other NRTIs require thymidine kinase, a zinc-dependent enzyme, for conversion to active triphosphate form. Moreover, HIV-infected populations tend to be zinc deficient. Conversely, elevated zinc status may not always be beneficial, and limited evidence suggests adverse effects in certain patients, especially at later stages of disease. Zinc coadministration appears to provide protective benefits, particularly in patients with diarrhea and opportunistic infections caused by Pneumocystis carinii and Candida . Further investigation warranted.
| Concomitant zinc may be appropriate if depletion occurs or deficiency develops. Monitor for clinical signs of zinc depletion with any long-term HAART therapy, especially AZT; lab tests often unreliable. Complement with low-dose copper with long-term zinc use.
| ADHD , Attention deficit–hyperactivity disorder; GABA , gamma-aminobutyric acid; AED , antiepileptic drug; HIV , human immunodeficiency virus; HAART , highly active antiretroviral therapy. |
Chemistry and Forms
Zinc acetate, zinc arginate, zinc ascorbate, zinc aspartate, zinc carbonate, zinc citrate, zinc gluconate, zinc glycerate, zinc glycinate, zinc histidinate, zinc lactate, zinc methionate, zinc monomethionine, zinc oxide, zinc picolinate, zinc selenate, zinc sulfate, zinc undecylenate.
Physiology and Function
Zinc is required throughout the human body for protein synthesis, DNA synthesis, cell division, hormonal activity, neurotransmitter signaling, and other critical functions. Zinc's essential role in many biological processes is illustrated by its participation in the activity of up to 300 enzymes, in all known classes. Although its activity in immune function has often received the greatest attention, zinc is required for normal physiological functioning of most body systems, particularly growth and development, neurological function, and reproduction, as well as numerous catalytic, structural, and regulatory functions at the cellular level.
Absorption of zinc occurs both by carrier-mediated and energy-dependent saturable processes and by simple (nonsaturable) diffusion throughout the length of the small intestine, primarily in the jejunum. Absorption is regulated homeostatically, in a range of 2% to 70%, depending on concomitant intake and zinc status in healthy individuals, and is optimal at an intragastric pH of 3 or less because solubility of zinc salts is affected by pH. Zinc is actively transported with albumin, amino acids, and an α2-macroglobulin; transport is regulated, in part, by sulfur-containing amino acids. Bioavailability is mainly influenced by zinc status and form; however, red wine, soy protein, and glucose can enhance zinc absorption, and iron, copper, calcium, fiber, and phytates (a component of cereal grain fiber) can inhibit absorption. Elimination of zinc is primarily through the feces, with minor amounts excreted through the urine and perspiration.
The average adult human body contains a total of 1.4 to 2.5 grams of zinc, with 60% to 65% stored in skeletal muscle, 30% in bone, particularly marrow, and 4% to 6% in the skin. The brain (especially the hippocampus and cerebral cortex) is the organ with the highest zinc concentrations, with enzymatic zinc (85%-95%) and synaptic zinc constituting two separate pools of brain zinc. Zinc is also found in relatively high concentrations in the eye (particularly iris, macula of retina, and choroid), liver, spleen, pancreas, kidney, prostatic fluid, and spermatozoa. Both red blood cells (RBCs) and white blood cells (WBCs) contain relatively high concentrations of zinc.
Zinc is a cofactor in the synthesis of proteins, fats, and cholesterol, and as a metalloenzyme activator, zinc is associated with the activity of more enzymes than any other mineral. Carboxypeptidase is necessary for the digestion of dietary proteins. Several dehydrogenases require zinc, including alcohol, retinol, and sorbitol dehydrogenase. Carbonic anhydrase, a zinc enzyme, catalyzes the interconversion of carbon dioxide (CO2) and bicarbonate (HCO3−) and thereby contributes to acid-base balance in RBCs. Cytochrome c is essential to electron transport and energy production. Superoxide dismutase (SOD), which contains both zinc and copper, inactivates free radicals in cytosol. Alkaline phosphatase (ALP) liberates inorganic phosphates for use in bone metabolism. The activity of these enzymes may be hampered by disruptions in zinc availability that are subclinical in degree (far short of frank deficiency) and conversely, are enhanced by increased zinc nutriture.
The immune, antioxidant, and detoxification systems require zinc, in ready availability and broad distribution, to maintain their functions at healthy levels. Immune function depends directly on zinc status in many ways through its central role in the production, regulation, activity, and equilibrium of both cellular and humoral immune responses, particularly as mediated by the thymus gland. Zinc participates in the regulation of a wide range of immune functions, including T lymphocytes, CD4 cells, natural killer (NK) T cells, interleukin-2 (IL-2), and SOD. As early manifestations of zinc deficiency, lymphopenia and thymic atrophy follow quickly on decreases in precursor T and B cells in the bone marrow, and IL-2 production by helper T (Th) lymphocytes will drop as lymphocyte proliferation decreases and cell-mediated immune function declines. Thus, decreases in available zinc may contribute to a premature transition from efficient Th1-dependent cellular immune activity to Th2-dependent humoral immune functions. The presence of adequate Zn2+and nitrogen oxide tilt the thymic balance toward Th1 and IL-2 as nitrogen oxide releases Zn2+from metallothionein, an intracellular storage molecule, and together they cooperate with glutathione (GSH) and GSSG, its oxidized form, to regulate immune responses to antigens. Conversely, a shift toward Th2 will be characterized by elevations in levels of IL-4, IL-6, IL-10, leukotriene-B4(LTB4), and prostaglandin E2(PGE2). Zinc is well known as a cofactor for SOD, a key antioxidant enzyme, but it also functions as a cofactor for alcohol metabolism and delta-6-desaturase (involved in PGE1synthesis). Among its activities in protecting against heavy metal toxicity, such as cadmium and lead, zinc's unique relationship with copper gives it a special capacity in countering toxic accumulation in Wilson's disease. Vitamin A levels are also regulated by a zinc-controlled release of hepatic stores.
Zinc plays diverse regulatory and support roles throughout the endocrine and reproductive systems as well as cell growth and differentiation processes. Proper functioning of genetic activities at many levels requires zinc, including the synthesis of DNA and RNA, protein synthesis, cellular division, and gene expression. Moreover, in its antioxidant capacity, zinc protects DNA from damage caused by oxidative stress. Zinc is necessary for the maturation of sperm, for ovulation, and for fertilization and normal fetal development. Zinc inhibits the activity of 5-alpha-reductase, the enzyme that irreversibly converts testosterone to dihydrotestosterone, a form that strongly binds to prostate tissue and thus contributes to hypertrophy. The hypogonadism observed in zinc deficiency may be related to impaired leptin secretion, which is also associated with zinc deficiency. Zinc promotes the conversion of thyroxine (T4) to triiodothyronine (T3) and enhances vitamin D activity. Thus, zinc plays a central role in normal growth and maturation, at cellular and systemic levels.
Synaptic zinc plays a modulatory role in synaptic neurotransmission. In the brain, zinc-containing neurons are found primarily in limbic and cerebrocortical systems. All neurons bearing synaptic zinc are glutamatergic. Synaptically released zinc plays a central role in brain excitability through modulation of ionic channels and amino acid receptors, including alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA), N-methyl-D-aspartate (NMDA), and gamma-aminobutyric acid (GABA) receptors. In particular, zinc acts as a potent antagonist of the glutamate-NMDA receptor. Zinc also induces brain-derived neurotrophic factor (BDNF) gene expression in the hippocampal/cortical neurons. Anorexia, dysphoria, impaired learning, diminished cognitive function, and other behavioral disturbances and mood disorders, as well as some neurological disorders (e.g., epilepsy, Alzheimer's disease), can be associated with zinc depletion and alterations of brain zinc homeostasis.
Zinc participates in the somatic interface with the environment through both the superficial tissues and the sensory organs. In addition to its presence in the skin and release through perspiration, the presence of zinc in the nails and hair is also notable (with deficiency indicated by leukonychia). Zinc's crucial role in skin health and wound healing is inherently related to its physiological and therapeutic activity in epithelial tissue. As mentioned, zinc is particularly concentrated in various components of the eye, where it is essential to dark adaptation and night vision. It also participates in the regulation of sensory perception through taste and smell. Not only is zinc crucial for taste perception, especially of salt, but taste response (or lack thereof) to zinc itself is predictive of deficiency status.
Known or Potential Therapeutic Uses
Proposed therapeutic and preventive uses of zinc range from the more common, and often self-prescribed, administration for prevention and mitigation of the common cold, treatment of acne and other dermatological conditions, enhancement of wound healing and immune response, to more clinical applications for high-risk mothers and malnourished infants, HIV and other viral infections, diminished fertility and reproductive gland function, gastric and bowel conditions, macular degeneration and other ophthalmologic diseases, and inflammatory processes such as rheumatoid arthritis. Notably, zinc administration can enhance muscular strength and endurance in healthy individuals, even in the absence of zinc deficiency. Pharmacological doses of zinc are administered for the treatment of acrodermatitis enteropathica (clinical zinc deficiency caused by congenital zinc malabsorption), to ascertain level of zinc absorption, and Wilson's disease, to prevent the copper accumulation in tissues. Effective treatment of mild or moderate zinc depletion typically requires months of zinc administration to reverse, and severe zinc depletion can require a year or more to resolve in some cases.
Historical/Ethnomedicine Precedent
Recorded use of zinc dates back to Egypt, circa 2000BCE, in the Western medical tradition. Known primarily for its use in skin lotions in both classical and folk traditions, its presence as zinc ore in calamine lotion is perhaps its most familiar form in recent popular memory and usage. Zincum metallicum and other forms of zinc were introduced into homeopathic medicine by Franz (1827), provings were conducted by Hahnemann (1839), and a large and systematic catalog of toxicology was assembled in the materia medica texts of Allen and others throughout the 1800s; these agents have been included in the official Homeopathic Pharmacopeia of the United States for more than 100 years. In the 1870s, W.H. Burt, a highly respected homeopathic physician, wrote: “Zinc corresponds to diseases of the nervous system, the same as Iron does to diseases of the blood.”
Although often selected because of their morphological similarity to male sexual organs (or “signature”), the recommendation of mussels (especially oysters and geoducks), seeds, and nuts as male tonics in many traditional systems of nutritional therapy may derive, at least in good part, from relatively high concentrations of zinc (and essential fatty acids). In pharmacognosy, the standard term for seed is semen, with both meanings related to substances rich in zinc.
Possible Uses
Acne vulgaris, acrodermatitis enteropathica, ageusia or hypogeusia (loss or diminishment of taste sensation), amenorrhea, anorexia nervosa, anosmia (lack of ability to smell), aphthous stomatitis (topical), athletic performance, attention deficit–hyperactivity disorder (ADHD), benign prostatic hyperplasia, birth defects (risk reduction), cataracts, celiac disease, cervical dysplasia, childhood intelligence (deficiency), cirrhosis (deficiency), common cold, contact dermatitis, Crohn's disease, cystic fibrosis, dermatitis herpetiformis (deficiency), diaper rash, diabetes mellitus (types 1 and 2), diarrhea (including with HIV), diverticulitis, Down syndrome, eczema, gastric ulcer healing, gastritis, halitosis, hepatitis, herpes simplex infection, HIV support, hypoglycemia, hypothyroidism, immune support/enhancement, infection, insulin resistance syndrome, lead and cadmium toxicity, macular degeneration, male infertility, male sexual function, minor injuries, night blindness, Osgood-Schlatter disease (with selenium), osteoarthritis, otitis media (recurrent), peptic ulcer, periodontal disease, pharyngitis, psoriasis, radiation therapy support, rheumatoid arthritis, sickle cell anemia, skin ulcers, thalassemia (deficiency), ulcerative colitis, warts, Wilson's disease, wound healing (oral and topical).
Deficiency Symptoms
Primary (dietary) zinc deficiency in humans was first described in patients with alcoholic cirrhosis (in 1956) and then in rural Iranian children and Iranian and Egyptian farmers with inadequate nutritional intake in the early 1960s. Primary deficiency has largely been considered a significant risk in individuals and populations with malnourishment or compromised physiology. However, awareness continues to grow as to the full extent of at-risk populations from a broad range of age groups, socioeconomic conditions, and living situations. Foods grown in nutrient-depleted soil and processed foods are often low in zinc. In addition to protein/calorie-restricted diets, potential deficiencies from diets replete with zinc-poor foods but limited in foods rich in highly bioavailable zinc are often aggravated by foods that are rich in inhibitors of zinc absorption. Infants, impoverished and elderly persons with poor nutritional status, and those consuming excessive alcohol or with renal and hepatic disease are clearly susceptible, but seemingly healthy individuals with unbalanced nutritional intakes, elevated demands, or adverse genetic characteristics may be equally at risk. Survey data indicate that more than 60% of adults (≥20 years) in the United States do not consume dietary zinc at the level of the recommended dietary allowance (RDA). Even by following the U.S. Department of Agriculture (USDA) food pyramid recommendations of the past several decades, an individual will not obtain adequate zinc intake on a daily basis. Moreover, some young women who avoid red meat contribute, at least in part, to their being both zinc and iron deficient. Thus, the typical diet in developed countries usually provides insufficient zinc for healthy function, with infants, adolescents, women, and the elderly at greater risk. The prevalence of primary zinc deficiency is estimated at 25% to 49% of the world's population.
Mild zinc deficiency is fairly common and can have a significant and pervasive impact within a short time. The supply of zinc within the human body operates with a small margin of error relative to metabolic needs. The very small amount of zinc that functions as the “exchangeable zinc pool” in the human body is sufficient for only a few days without intake. Even with the relative inaccessibility of zinc deposits in bone or muscle tissue, excess zinc intake in the short-term is not usually retained (because of decreased absorption or rapid excretion). Consequently, consistent zinc intake is essential to maintain zinc metabolism within the narrow parameters between healthy function and systemic repercussions of insufficiency. Thus, a zinc-poor diet, poor assimilation, interfering agents, and an increase in physiologic demands can result in adverse effects within a short period. Nevertheless, scientific knowledge of the pathogenic mechanisms and complete characteristics of zinc deficiency remain incomplete.
A wide range of conditions can contribute to compromised zinc nutriture, insufficiency, and conditioned (secondary) deficiency. Acrodermatitis enteropathica is an inherited (autosomal recessive) disease characterized by zinc malabsorption and resulting in eczematoid skin lesions, alopecia, diarrhea, and concurrent bacterial and yeast infections. The life stages characterized by rapid growth, particularly pregnancy and lactation, childhood, and adolescence, are potentially as vulnerable as the hospitalized or institutionalized elderly person. Multiple pregnancies or shifts in growth rate, as well as infection or malignancy, can further aggravate disequilibrium in zinc metabolism. Likewise, deficient zinc intake can occur with chronic dieting, as well as poorly planned vegan, vegetarian, and semivegetarian diets. Excessive iron, calcium, or grain intake, particularly with simultaneous ingestion, may also interfere with zinc absorption, particularly because of phytic acid content of cereal grains. Impaired zinc absorption also occurs in individuals with gastrointestinal (GI) disorders, including diarrhea, pancreatic insufficiency, celiac sprue or other malabsorption syndromes, inflammatory bowel disease, Crohn's disease, and ulcerative colitis. Likewise, injuries or inflammatory conditions, such as burns, wound healing, dermatitis, rheumatoid arthritis, and chronic inflammatory diseases, that increase interleukin-1 (IL-1) can rapidly deplete available zinc due to increased utilization, thus producing short-term adverse effects. Hemorrhage, hemolytic anemias (e.g., sickle cell disease, thalassemia), superficial losses, excessive diuresis, or GI tract wastage into stool can also produce rapid zinc loss sufficient to cause systemic problems. Renal insufficiency predisposes to excess zinc excretion. Macular degeneration, type 2 diabetes mellitus, malignant melanoma, congestive heart failure, and other degenerative conditions are also associated with zinc deficiency. The variety of conditions that can adversely affect zinc status, together with the delicate balance of zinc available within the human organism, render zinc nutriture critical and the consequences of deficiencies pervasive and potentially significant.
The classic clinical presentation of severe zinc deficiency is characterized by diarrhea, poor wound or ulcer healing, dermatitis, psychiatric disturbances, weight loss, intercurrent or recurrent infection, alopecia, and hypogonadism (in males). Immunodepression, muscle pain, and fatigue are also among the first and most important signs and symptoms of zinc deficiency, and immune function can be depressed in humans with even mild zinc deficiency. In general, any rapidly growing cells can be affected in initial stages. Thus, compromised health of epithelial tissues, manifesting as impaired wound healing, dermatitis, rough skin, inflammatory acne, poor nail health, increased incidence of infections, diminished immune response, and elevated intolerance to environmental toxins may also indicate impaired zinc status. Anosmia and reduced taste acuity can also suggest zinc deficiency and may manifest only through poor appetite. Photophobia, night blindness, nystagmus, or decline in visual acuity may signal diminished zinc availability affecting the eyes, resulting, at least in part, from decreased ability to mobilize retinol from the liver. Diminished fertility, particularly with impaired spermatogenesis or ovulation, menstrual irregularities, weight loss, impaired glucose tolerance, and increased lipid peroxidation are among the predictable but often-unrecognized consequences of deficiencies in physiological functions dependent on zinc nutriture. Also less obvious, but more insidious in outcomes, are longer-term changes that can result from poor zinc status, such as slow or stunted growth and delayed puberty or other sexual development, as well as irritability, anxiety, depression, difficulty with concentration and cognitive function, impaired learning, or other psychoneurological conditions. Zinc deficiency before and during pregnancy may contribute to intrauterine growth retardation and congenital fetal abnormalities. In rat studies, zinc deficiency during pregnancy results in lifelong immune abnormalities in the offspring despite adequate zinc intake from birth, which requires three generations of normal zinc nutriture to reverse.
Dietary Sources
Seafood and red meat (especially liver and other organ meats) are the richest dietary sources of zinc, with a single oyster providing about 8 to 15 mg zinc. Poultry and eggs provide moderate amounts of dietary sources of zinc. Whole grains, nuts, and seeds provide smaller amounts of zinc, ranging from 0.2 to about 3 mg per serving, with notable sources being sunflower and squash seeds, wheat germ, hard-wheat berries, wheat bran, buckwheat, rice bran, millet, whole-wheat flour, oatmeal, brown rice, cornmeal, and sprouted grains. However, the zinc in plant foods, particularly whole-grain cereals and soy protein, can bind to phytic acid to form an insoluble zinc-phytate complex and thus is usually less bioavailable. Breads, breakfast cereals, and nutrition bars are often fortified with substantial amounts of zinc. Other food sources of zinc include hard cheese, peanuts, soy meal, black-eyed peas, green beans, chickpeas, lima beans, spinach, green onion, and green leafy vegetables. In general, food processing removes or destroys a high proportion of zinc, as well as other trace elements. The presence of certain amino acids, such as cysteine and histidine, may enhance absorption of zinc from foods.
Nutrient Preparations Available
Numerous forms of zinc are available, as previously listed. Zinc sulfate is an inexpensive form most often used in clinical trials. Many experienced practitioners of nutritional therapeutics, however, prefer to administer organically bound or chelated forms (e.g., zinc acetate, zinc citrate, gluconate, zinc glycerate, zinc monomethionine, zinc orotate, zinc picolinate, zinc-protein hydrolysate), based on a lower incidence of gastric irritation and (presumed) superior bioavailability and utilization. In general, zinc acetate provides the most bioavailable form of zinc, across a broad range of gastric pH.
Lozenges generally contain zinc gluconate, zinc gluconate-glycinate, or zinc acetate. The efficacy of various lozenges correlates with their relative iZn dosage, the sum of all positively charged (ionized) zinc species for zinc compounds at physiologic pH of 7.4. Although all others forms are available over the counter (OTC) as nutritional supplements, zinc acetate is considered a prescription item because of its use in the treatment of Wilson's disease, although zinc acetate lozenges are available as an OTC drug for upper respiratory infection (URI) treatment.
The various forms of oral zinc are salts with differing zinc content. For example, zinc sulfate contains 23% elemental zinc and zinc gluconate 14.3% elemental zinc. Thus, the amount of zinc in some typical supplemental forms is as follows: zinc amino acid chelate, 100 mg/g; zinc gluconate, 130 mg/g; zinc orotate, 170 mg/g; and zinc sulfate, 227 mg/g. A typical zinc sulfate dose of 220 mg provides approximately 55 mg of elemental zinc. However, solubility and ionizability of the various salts of can have major impact on bioavailability.
Dosage Forms Available
Capsule, injectable, intranasal gel, intranasal spray, liquid, lozenge, tablet, topical. Parenterally, zinc is usually included as a component of total parenteral nutrition (TPN).
For optimal absorption, oral zinc should usually be ingested between meals. However, if adverse GI effects occur, consumption with meals may be adequate and effective. In general, oral zinc intake should be separated from ingestion of high-fiber foods to minimize impairment of absorption, as well as high-dose calcium or iron supplements. Likewise, the antiviral activity of zinc lozenges may be impaired by certain flavorings, sweeteners, or other additives.
Source Materials for Nutrient Preparations
Zinc acetate and zinc chloride are derived from mineral salts consisting of zinc and chloride or zinc nitrate and acetic anhydride, respectively. Zinc carbonate is derived from smithsonite or zincspar. Chelates such as zinc citrate, zinc gluconate, zinc lactate, zinc orotate, zinc picolinate, and zinc selenate are derived from smithsonite or other rock processed with citric acid, gluconic acid, lactic acid, orotic acid, picolinic acid, or selenic acid, respectively. Zinc oxide is derived from zincite and zinc phosphate from hopeite.
Dosage Range
The issue of zinc dosage is unclear and eludes scientific knowledge necessary to establish a basis for widely agreed conclusions. Dietary supplements typically contain 5 to 50 mg (elemental zinc) per daily dose. Moderate intake of 15 to 50 mg daily can be used safely to provide for physiological requirements and prevent deficiency. Short-term, repeated use of zinc lozenges containing higher doses (e.g., 13-25 mg each), with up to 10 lozenges daily, is generally well tolerated for several-day periods. Therapeutic application of zinc at 50 mg, one to three times daily, may be appropriate for certain conditions, such as copper overload in Wilson's disease, under the supervision of a health care professional. The presence of zinc in some fortified foods may alter the equation for any given individual based on consumption, but is often offset by impaired bioavailability resulting from certain dietary constituents and how they affect certain forms of zinc.
Adult
- Dietary: The U.S. RDA for zinc is 15 mg per day for adult men and 12 mg per day for adult women, but average daily intake in developed societies is typically only 60% to 70% of that amount, with the average adult daily diet in the United Kingdom providing 11.7 mg for men and 8.7 mg for women. The official U.S. recommendations for daily intake in pregnant women is 11 mg (13 mg if ≤18 years old) and 12 mg for nursing women (14 mg if ≤18 years old).
- Supplemental/Maintenance: 15 to 50 mg per day, preferably with copper.
In some respects, however, zinc intake beyond adequate dietary intake is sometimes considered inappropriate unless indicated, given “almost no gap for supplementation” above the RDA and the reference dose (RfD) for safe intake of zinc, although, as noted, usually a gap exists between average daily dietary intake and the recommended daily intake. Few data are available on optimal zinc intakes (as assessed by function of zinc-dependent enzymes in free-living human subjects), and it is likely that optimal intakes vary considerably depending on age, lifestyle, and various states of health and disease.
Pharmacological/Therapeutic: 50 to 350 mg (elemental zinc) per day.
Oral doses as high as 220 mg zinc sulfate three times daily have been used in trials of zinc for the prevention of crisis in sickle cell anemia, and twice daily for 12 weeks to correct zinc deficiency in cirrhotic patients with symptoms of deficiency (e.g., blunted taste/smell). In a trial involving patients with chronic fatigue syndrome, 135 mg/day was administered for 15 days (along with 2 mg copper daily) to correct zinc deficiency.
- Toxic: Toxicity can occur at levels as low as 60 mg/day (with prolonged intake) but is more frequently associated with doses higher than 300 mg/day. Prolonged intake at doses higher than 150 mg/day may be associated with adverse effects. The official U.S. tolerable upper limit (UL) for adults (≥19 years) is 40 mg, including pregnant or nursing women, although it is 34 mg/day if such women are 18 years old or younger. This amount includes dietary intake and thus may vary considerably with high consumption of fortified foods or foods naturally rich in zinc.
Pediatric (<18 Years)
Dietary: Zinc concentrations in breast milk are relatively low, but such zinc is highly absorbable. Official U.S. recommendations for daily intake follow :
- Infants, birth to 6 months: 2 mg/day
- Infants, 7 to 12 months: 3 mg/day
- Children, 1 to 3 years: 3 mg/day
- Children, 4 to 8 years: 5 mg/day
- Children, 9 to 13 years: 8 mg/day
- Adolescents, 14 to 18 years: 9 mg/day for females; 11 mg/day for males
Clinical experience with adolescents suggests that much larger amounts may be required during growth spurts (up to 40 mg/day).
- Supplemental/Maintenance: Usually not recommended for children under 12 years of age with healthy, balanced diet, without excessive dietary phytates.
- Pharmacological/Therapeutic: 5 to 40 mg per day, for specified periods.
Trials investigating zinc supplementation in infants born small for gestational age (SGA) typically use 5 mg zinc sulfate daily, often combined with other nutrients. Zinc acetate (10 mg twice daily for 5 days) has been used successfully in infants and young children with severe acute lower respiratory infection. Several prominent trials have found efficacy of low-dose oral zinc in acute and persistent diarrhea in children under 5 years of age in developing countries.
- Toxic: 150 mg/day on a chronic basis, or acutely with doses greater than 200 mg daily. However, the toxic dose of zinc depends primarily on dose and duration, and also varies with status and absorption, weight, and concomitant intake. Single intravenous (IV) doses of 1 to 2 mg zinc/kg body weight have been given to adult leukemia patients without toxic manifestations. Consensus as to toxic dose in clinical applications has not been established, and plasma levels sufficient to produce symptoms of toxic manifestations are not known.
Tolerable upper intake levels (UL) for zinc follow :
- Infants, 0 to 6 months: 4 mg/day
- Infants, 7 to 12 months: 5 mg/day
- Children, 1 to 3 years: 7 mg/day
- Children, 4 to 8 years: 12 mg/day
- Children, 9 to 13 years: 23 mg/day
- Adolescents, 14 to 18 years: 34 mg/day
Laboratory Values
Overview
Clinicians and researchers broadly agree that clinical presentation and response to zinc administration provide the most accurate means of assessing zinc status and confirming deficiency status. Thereafter, retesting (e.g., plasma zinc) and reevaluation of symptoms after 4 to 6 months of treatment are usually effective for determining if dosages need adjustment. In a review, Hambridge (2003) concluded that there is a “compelling demand for improved zinc biomarkers” based on numerous characteristics peculiar to the physiology of zinc in the human organism. “More specific markers of zinc status are needed, and their relationships to zinc-dependent cellular functions and the distribution and allocation of zinc to the different organ systems need to be clarified.” Some physicians experienced in nutritional therapeutics consider measuring the leukocyte zinc level as the best laboratory method for determining zinc status. Most clinicians and researchers do not consider hair a reliable form of analysis for measuring tissue levels of zinc. Moreover, some clinicians observe that urine and hair tissue levels are often elevated in patients with zinc deficiency because of dysfunction in zinc metabolism and high rates of excretion.
Erythrocyte Zinc
Most of the zinc measured as erythrocyte zinc is incorporated in carbonic anhydrase. Although some studies report detection of depletion through low levels, erythrocyte zinc has been generally regarded as not readily depleted and therefore not accurately indicative of zinc status.
Hair Zinc
Some clinicians have suggested that analysis of hair zinc concentrations might reveal associations between low hair zinc levels and zinc depletion status. However, numerous factors, such as age, growth rate, and dietary intake of phytates and meat, can confound analysis and decrease this test's ability to consistently determine impaired zinc status or inadequate intake. Antidandruff shampoos often incorporate zinc as well, which can greatly elevate hair zinc levels.
Plasma Zinc
The range for normal plasma levels for zinc is 58 to 106 µg/dL. In blood plasma, zinc is bound to albumin (80%) and to α2-macroglobulin (20%). Plasma zinc levels appear to follow a circadian rhythm, with the highest values occurring late morning, at approximately 10AM. Plasma zinc can be normal even when plasma albumin is low, because albumin normally contains many unsaturated binding sites.
Plasma zinc and serum zinc are often used in clinical and research settings but are physiologically insensitive and of limited diagnostic value. Hambridge observed: “Plasma zinc is currently the most widely used and accepted biomarker of zinc status despite poor sensitivity and imperfect specificity…. One reason that plasma zinc does not accurately reflect the volatile relationship between zinc intake and absorption is that homeostatic control of plasma zinc concentrations can occur while moderate changes are occurring in the zinc content of one or more of the pools of zinc that exchange rapidly with zinc in plasma.” Furthermore, the decline that occurs as a recognized component of the acute-phase response in infections represents at least one important limitation affecting the specificity of plasma zinc as an index of zinc status. Severe acute zinc deficiency states, such as untreated acrodermatitis enteropathica, may reveal profoundly depressed plasma zinc levels. However, mild zinc deficiencies that can adversely affect physiological function may appear as plasma zinc concentrations within the normal range, as with growth-limiting zinc deficiency states in young children. Various studies have conflicting findings and mixed conclusions regarding an association between zinc intake and plasma zinc. Nevertheless, concentrations less than 70 µg zinc/dL plasma can serve as a useful predictor of growth response to zinc supplementation, and beneficial effects of zinc administration in the prevention and management of diarrhea can be predicted using lower cutoff values. Plasma levels less than 70 µg/dL might constitute a better definition of deficiency state.
Red Cell Membrane Zinc
Metallothionein levels in erythrocytes respond to administration of zinc as well as restricted dietary intake. Thus, RBC membrane zinc may be a sensitive indicator of zinc depletion, but its practical implementation on a widespread basis is considered unlikely given the complexity of sample preparation. A parallel situation appears with monocyte, neutrophil, or platelet zinc.
Serum Zinc
Serum zinc concentration less than 33 µg/dL indicates zinc deficiency. Serum levels 33 to 50 µg/dL indicate marginal zinc status. The normal range for serum zinc is 67 to 124 µg/dL, although this varies between clinical laboratories.
Serum zinc is considered an insensitive marker of physiological zinc status, for the same reasons previously stated in relationship to plasma zinc.
White Blood Cell Zinc
The levels of zinc in leukocytes or lymphocytes appears to reflect zinc status accurately, particularly in relation to key zinc-related functions such as immune function, life stage, and growth processes. For example, leukocyte (WBC) zinc is reflective of fetal growth and associated with maternal muscle zinc concentration. Likewise, activity of lymphocyte ecto-5′-nucleotidase is a sensitive indicator of zinc status.
Assessment of gene expression of zinc-dependent genes in lymphocytes (specifically cellular zinc transporter hZip1) offers promise as a biomarker of expression of the cellular zinc response to zinc intake and bioassay for zinc status.
Zinc Tally
In this quick and simple screening method for evaluating zinc status, the absence of the typical metallic taste of zinc, after placing 2 teaspoons of a 0.1% solution of zinc sulfate heptahydrate in the patient's mouth and holding it there for 10 seconds, suggests deficiency. An immediate taste perception indicates that zinc status may be adequate; conversely, lack of zinc taste suggests deficiency.
Zinc Tolerance Test
In this test an oral load of 50 mg elemental zinc is administered, after a baseline plasma zinc measurement, and plasma zinc is remeasured 120 minutes later. A twofold to threefold increase in plasma zinc indicates zinc deficiency. Zinc supplements need to be avoided for 24 hours before sampling of plasma.
CD4+/CD8+ T-Lymphocyte Ratio and Thymulin Activity
The CD4+/CD8+ T-lymphocyte ratio and thymulin activity have been advanced as potential immunological tests for zinc deficiency, but evidence confirming their accuracy is lacking.
Other findings possibly consistent with zinc insufficiency, but also resulting from other causes, include the following :
- Elevated anserine and carnosine peptides, with low levels of essential amino acids, in urine or plasma amino acid analysis.
- Elevated phosphoserine and phosphoethanolamine in urine amino acid analysis.
- Elevated lactic acid in plasma or urine (lactic acid dehydrogenase also is zinc dependent).
- Elevated or normal linolenic acid, but low gamma-linolenic acid, consistent with weak delta-6-desaturase activity (zinc dependent).
Overview
Zinc dosage beyond the RDA is not established, and the perpetually marginal nature of zinc nutriture leaves a relatively small dosage range and tight time frame for safe and effective use of zinc between suboptimal and potentially toxic intake levels, particularly with extended use outside a balanced nutrient regimen. The affinity of zinc for certain tissues appears to result in a pattern of benefit and toxicity converging (e.g., immune system, possibly prostate). The dose typically used for short-term immune stimulation as a lozenge (13-25 mg each) would be excessive for continued use with oral intake and could impair immune function (at >150-300 mg/day). Likewise, 25 to 30 mg daily has been used to improve pregnancy outcomes in low-income pregnant women and pregnant teenagers, but a significantly higher dose could have potentially adverse effects during pregnancy, especially on embryogenesis.
Zinc is perhaps the least toxic mineral nutrient at usual doses but can be strikingly toxic at very high doses associated with industrial exposure. Notably, major authorities on zinc physiology, requirements, and safety acknowledge the limited scope of scientific knowledge as to its physiological functions, the multiple variables affecting bioavailability, dynamic relationships between zinc and other minerals, parameters governing insufficiency and toxicity, and methods of assessing functional zinc levels.
Nutrient Adverse Effects
General Adverse Effects
Zinc is generally considered relatively nontoxic at low to moderate levels typical of supplemental use: less than 50 mg elemental per day. Given the narrow gap between potentially insufficient and excessive levels, both deficiency and toxicity can vary significantly among individuals based on tissue and circulating levels, historic intake, zinc pool status, recent or active infection, blood loss or other depletion factors, dietary interactions, and other variables. Gastrointestinal upset and nausea are quite common when zinc supplements, especially zinc sulfate, are taken on an empty stomach. More importantly, zinc administration, especially lacking in compensatory copper support, can produce adverse effects rapidly (as with deficiency), which grow in intensity based on dose and duration and influenced by other variables. The primary toxic effects of zinc, typically associated with prolonged intake at levels greater than 150 mg daily, include copper deficiency anemia, depressed immune function, and reduced high-density lipoprotein (HDL) cholesterol levels.
Topical zinc preparations are generally considered safe and unlikely to produce any adverse effects. However, anosmia has been reported with zinc nasal spray and in rare cases has been reported to be severe or permanent.
The primary effects of zinc toxicity can occur with doses higher than 150 mg/day on a chronic basis or acutely with doses greater than 200 mg daily. They include diarrhea, nausea, vomiting, metallic taste in the mouth, dizziness, drowsiness, incoordination, and lethargy. Gastric erosion and hematuria with chronic high-dose use have been reported but not confirmed. Ingestion of 10 to 30 g of zinc sulfate can be lethal in adults. However, acute zinc toxicity is extremely rare because ingestion of the amounts required for toxicity symptoms (2 g/kg) will usually provoke vomiting before toxic dose levels are attained. Impairment of copper absorption can begin at daily doses as low as 50 mg elemental zinc, with copper depletion accruing over time and manifesting as low serum copper and ceruloplasmin levels, microcytic anemia, and neutropenia; iron deficiency is also possible. Immune function can become impaired, HDL cholesterol levels decrease, and total cholesterol levels increase with daily doses over 300 mg/day for extended periods, but possibly as low as 150 mg/day, perhaps as a result of induced copper deficiency. Subsequently, zinc-induced copper deficiency has been associated with cases of reversible acquired sideroblastic anemia, cardiac arrhythmias, and bone marrow depression. Such reports have involved chronic intake of 450 to 1600 mg daily, and many such cases are properly characterized as zinc abuse, with ingestion of coins being the source of zinc in one individual. Inhalation of zinc oxide in certain industrial settings and the use of galvanized pipes for drinking water are also known causes of excess zinc exposure.
Short-term frequent use of zinc lozenges can occasionally produce digestive upset, local oral irritation, and unpleasant taste; typically reversible with cessation.
Adverse Effects Among Specific Populations
One study from India suggests that the concomitant use of zinc and oral antibiotics in the acute management of pneumonia of infants or children may delay recovery during the hot season, particularly in the absence of zinc deficiency.
Two preliminary papers by Bush et al. discussed the possibility of zinc aggravating amyloid formation in individuals with Alzheimer's disease. However, subsequent research articles and reviews have concluded that zinc does not cause or exacerbate Alzheimer's disease symptoms, and may enhance mental function by improving platelet membrane microviscosity.
Genotoxicity
“Zinc is apparently neither a mutagen nor a carcinogen.” However, in one study analyzing data from a larger trial, researchers reported a slight increase in the relative risk of prostate cancer among men who used zinc supplements for more than 10 years, particularly at doses greater than 100 mg elemental zinc daily.
Pregnancy and Nursing
Maternal nutritional zinc deficit “can have permanent negative effects on the growth of offspring,” and zinc administration at typical dose levels may be beneficial during pregnancy. However, excess zinc intake “during embryogenesis can be teratogenic or lethal,” and premature birth and stillbirth have been reported when women consumed 100 mg three times daily during the third trimester. The use of supplemental zinc by nursing mothers over an extended period, without compensatory copper support, could contribute to zinc-induced copper deficiency in breastfed infants. Nevertheless, no reports or studies in the scientific literature show any adverse effects on fetal development from supplemental zinc, at typical doses, in well-nourished mothers or in infants who are breastfed.
Contraindications
No contraindications have been established for zinc.
Precautions and Warnings
Extended use of zinc without copper carries a warning. The recommended ratio of zinc to copper is 15:1 to 20:1. This ratio is higher in elderly persons, who, in the United States, tend to have high copper levels and low zinc levels because of a history of chronic ingestion of water carried through copper pipes.
Strategic Considerations
Three simple and consistent themes are recurrent among the various interactions between zinc and pharmacological agents. First, as a mineral/metal, zinc tends to chelate with many substances when ingested simultaneously or in temporal proximity. This potential problem is easily avoided through patient education and clinical management; individuals should separate intake, preferably taking zinc at least 2 hours before or 4 hours after such medications. Second, in all situations except the treatment of individuals with Wilson's disease, the default prudent measure with any long-term application of zinc is to avoid zinc-induced copper deficiency by periodically monitoring serum copper levels and coadministering low-dose copper (1-3 mg/day). Third, within the human organism, zinc is volatile with an ever-shifting distribution between pools. Thus, establishing zinc deficiency or monitoring the impact of any agent on functional zinc status is difficult and unreliable. Consequently, at usual dosage levels and with attentiveness to clinical manifestations of zinc deficiency (or excess), coadministration of zinc within a therapeutic strategy carries minimal risk of adverse interactions, other than copper depletion and the predictable chelation phenomena common to most minerals when ingested with other substances.
Numerous pharmaceutical agents are associated with adverse effects, both subtle and overt, of zinc depletion. Consequently, numerous clinical situations occur in which coadministration of zinc may improve zinc nutriture, related physiological functions, and clinical manifestations, even when prior conventional laboratory assessment had revealed no measurable signs of depletion, insufficiency, or deficiency. These recurrent patterns indicate two probable phenomena: zinc can provide benefit in the absence of depletion, detected or not, and conventional laboratory methods currently applied for assessing zinc status are insensitive and inadequate to clinical demands. Our limited knowledge of the many functions of zinc is repeatedly revealed in the sparsity and limited depth of both the observations of zinc-related benefits and interactions and the mechanisms involved.
Many widely used pharmaceutical agents contribute to zinc depletion, usually through binding and increased urinary zinc excretion. Thus, coadministration of zinc may reduce depletion effects or prevent other adverse effects associated with a wide range of medications used to treat hypertension, inflammation, and other conditions. Particularly with chronic use, thiazide diuretics increase urinary zinc excretion, as do loop diuretics, although probably to a lesser degree. Although patients treated with angiotensin-converting enzyme (ACE) inhibitors (especially captopril) at clearly are risk for zinc depletion, the effects of potassium-sparing diuretics on zinc are diverse and complicated. Furthermore, amiloride is often combined with a thiazide diuretic to reduce mineral loss, but amiloride may cause zinc accumulation by reducing urinary excretion. In contrast, triamterene can increase urinary zinc excretion in the short-term and cause depletion with extended use. In patients treated with antacids and gastric acid–suppressive medications, long-term drug therapy can impair zinc absorption and reduce availability by interfering with the normal acid environment of the stomach; although cimetidine appears to be an exception among H2blockers. With these drugs, administration of zinc can prevent or reverse depletion and enhance healing of gastric tissue damaged by ulceration. When coadministered with nonsteroidal anti-inflammatory drugs (NSAIDs), zinc may reduce risk of adverse effects on zinc status while providing protective effects and contributing to enhanced therapeutic outcomes.
Oral corticosteroids and valproic acid, alone or in combination with other anticonvulsant agents, represent examples of medications that can deplete zinc, but for which evidence of benefit from concomitant zinc is limited or lacking.
Evidence of variable strength suggests a probable synergy or other benefit from concomitant zinc administration with a wide range of conventional interventions, including mixed amphetamines, androgens, clobetasol (and potentially other topical corticosteroids), metronidazole (in treating trichomoniasis), and chlorhexidine-zinc oral rinse. In the treatment of individuals with Wilson's disease, concomitant zinc may enhance the therapeutic activity of penicillamine in reducing copper levels, although intake needs to be separated. Zinc therapy can be applied to reduce adverse effects to taste sensation in patients receiving radiation therapy, particularly to the head and neck.
In several areas the coadministration of zinc with conventional therapies appears to produce mixed effects, depending on patient characteristics, with full implications as yet unclear. For example, in women of reproductive age, oral contraceptives may decrease serum levels of zinc; conversely, osteoporotic postmenopausal women taking conjugated estrogens and medroxyprogesterone may exhibit reductions in previously elevated urinary zinc excretion. Zidovudine (AZT) and related antiretroviral agents present another complicated situation where divergent responses are common. In a patient population often characterized by zinc insufficiency, zinc coadministration may reduce drug-related adverse effects, add protective benefits (particularly in patients with diarrhea and opportunistic infections), provide no significant benefit, or even potentially elevate the risk of complications.
Numerous clinical situations allow for possible synergy, particularly in individuals or populations at greater risk for compromised zinc or broader nutritional status. The areas of antibiotic therapy, oral or topical, and antidepressant medications, particularly tricyclic and selective serotonin reuptake inhibitor (SSRI) antidepressants, offer significant potential for continued research into integrative therapeutic applications.
In many situations, zinc (as well as most other minerals) tends to bind with other substances and thereby decrease bioavailability and therapeutic action or nutritive value of both agents. Separation of intake remediates this problem. Antibiotics from the tetracycline class (other than doxycycline) or fluoroquinolone class (particularly ciprofloxacin) and warfarin or related oral vitamin K antagonist anticoagulants stand as primary examples of situations commonly accepted as involving a significant risk of pharmacokinetic interference.
Zinc may play a central role in the intimate relationships between the immune system and the mental-emotional states traditionally ascribed to the central nervous system (CNS). The body of scientific knowledge emerging within the field of psychoneuroimmunology may render obsolete conventional parsing of academic disciplines, which often are inadequate in conveying the totality of complex physiological functioning inherent in clinical medicine. A more comprehensive model can provide a forum for further research into the broader functions of zinc that transcend narrow categorization and defy reductionist analysis.
Amphetamine (amphetamine aspartate monohydrate, amphetamine sulfate), dextroamphetamine (dextroamphetamine saccharate, dextroamphetamine sulfate; D-amphetamine; Dexedrine). - Mixed amphetamines: amphetamine and dextroamphetamine (Adderall; dexamphetamine).
Extrapolated, based on similar properties: Methylphenidate (Metadate, Methylin, Ritalin, Ritalin-SR; Concerta). | Beneficial or Supportive Interaction, Not Requiring Professional Management |
Probability:
2. Probable or 3. PossibleEvidence Base:
Preliminary, maybe EmergingEffect and Mechanism of Action
Zinc nutriture and physiology are important in mood and brain function and may play an independent role in physiology related to attention deficit–hyperactivity disorder (ADHD), particularly in individuals of older age and higher weight with low zinc and free fatty acids levels. Mechanisms apart from correcting zinc deficiency have not been investigated or elucidated. However, data derived from research into depression and CNS function are relevant. In particular, zinc plays an important role in neurotransmission in the brain by modulating the activity of glutamate and gamma-aminobutyric acid (GABA) receptors. Furthermore, hippocampal and cortical neurons, noted for high concentrations of zinc, “possess mechanisms for Zn 2+ uptake and storage in synaptic terminals” and for stimulation of release of Zn 2+ ions along with neurotransmitters. “Zn 2+ modulates predominantly the excitatory (glutamatergic) and inhibitory (GABA-ergic) amino acid neurotransmission pathways in CNS.”
Research
Limited research suggests that zinc may provide independent benefit in patients with ADHD and may complement conventional therapy using mixed-amphetamine salts. Studies have suggested a correlation between zinc deficiency and pathophysiology of ADHD. In a double-blind, placebo-controlled study involving 400 children (72 girls, 328 boys, mean age 9.61 years), Bilici et al. found that zinc sulfate (150 mg daily for 12 weeks) was “significantly superior to placebo in reducing symptoms of hyperactivity, impulsivity and impaired socialization in patients with ADHD. However, full therapeutic response rates of the zinc and placebo groups remained 28.7% and 20%, respectively.” The authors added that “the hyperactivity, impulsivity and socialization scores displayed significant decrease in patients of older age and high BMI score with low zinc and free fatty acids (FFA) levels.” In a paper published later that same year (2004), Akhondzadeh et al. reported findings from a 6-week, double-blind, randomized trial involving 44 children (26 boys and 18 girls), age 5 to 11 years, comparing methylphenidate (1 mg/kg/day) plus zinc sulfate (15 mg elemental zinc daily) to methylphenidate plus placebo in the treatment of ADHD. Outcomes, as assessed using Parent and Teacher ADHD Rating Scale scores, “improved with zinc sulfate,” and the difference between the two protocols was significant, “as indicated by the effect on the group, the between-subjects factor.” The difference in frequency of adverse effects between the two groups was “not significant.” The authors concluded that their findings demonstrated that zinc coadministration “might be beneficial in the treatment” of children with ADHD, and that further investigations using different doses of zinc are required to replicate these findings.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians treating individuals diagnosed with ADHD are advised to consider nutritional support independently or in concert with the pharmacological therapies, such as methylphenidate or mixed amphetamines. The evidence for benefit from zinc is positive but limited, and use would generally be considered as a component of a broader nutritional strategy rather than adequate as a monotherapy. Nevertheless, the use of concomitant zinc at a low dosage level, 10 to 40 mg elemental zinc daily depending on weight and age, may be beneficial and is generally safe and unlikely to produce clinically significant adverse effects.
Health care professionals experienced in nutritional therapies typically emphasize reduced sugar intake and other blood glucose stabilization measures, removal of artificial additives (especially dyes) from diet, observation of intolerance to potentially reactive foods, and coadministration of nutrients, on a personalized basis, such as essential fatty acids (eicosapentaenoic acid [EPA], docosahexaenoic acid [DHA], gamma-linolenic acid [GLA], linoleic acid), oligomeric proanthocyanidins (e.g., pine bark, grape seed extract), magnesium, chromium, L-carnitine, and B vitamins.
Fluoxymesterone (Halotestin); testosterone cypionate; methyltestosterone (Android, Methitest, Testred, Virilon). Related but evidence lacking for extrapolation: Methyltestosterone combination drug: methyltestosterone and esterified estrogens (Estratest, Estratest HS); testolactone (Testolacton; HSDB 3255, SQ 9538; Fludestrin, Teolit, Teslac, Teslak). | Beneficial or Supportive Interaction, with Professional Management |
Probability:
3. PossibleEvidence Base:
PreliminaryEffect and Mechanism of Action
Various androgens are administered clinically for treatment of diverse conditions. Zinc plays a key role in normal male sexual development, prostate function, and the maturation of sperm, as well as ovulation and fertilization. Further, zinc deficiency can cause hypogonadism, with a possible contribution from impaired leptin secretion. Zinc may raise serum testosterone and dihydrotestosterone levels and sperm counts in some men, particularly those with low sperm counts, possibly by stimulating testosterone production in Leydig cells.
Coadministration of zinc during androgen treatment (e.g., infertile men with insufficient sperm motility) may enhance the efficacy of treatment, and in fact, zinc appears to be essential for such functions. The mechanisms of action involved in this synergistic interaction have not been fully elucidated.
Research
Limited evidence from clinical trials indicates that coadministration of zinc with androgens may enhance therapeutic outcomes, particularly in males with low baseline zinc levels. Castro-Magana et al. investigated the role of zinc in boys with constitutional growth delay, familial short status, and delayed appearance of secondary sexual characteristics. They measured hair and serum zinc levels in boys with growth delay and short status initially and then again after administering methyltestosterone. They determined that “zinc levels in boys beyond stage 3 of genital development are significantly higher than in stage 1 and 2,” and they observed “a linear relationship between zinc levels and serum testosterone concentration (up to 250 ng/dL).” Moreover, they found that “methyltestosterone administration raised the zinc concentration in serum and hair, especially in boys with constitutional growth delay.” Thus, a synergistic relationship between zinc and testosterone function was suggested, in that “increased endogenous production or exogenous supply of testosterone [is] associated with increased zinc levels.” These authors concluded that “the relative testosterone deficiency and hypogonadotropism seen in constitutional growth delay may result in decreased zinc levels, which in turn could cause a further delay in the appearance of secondary sexual characteristics and greater growth retardation.”
Subsequently, Takihara et al. compared the effects of 3 months of zinc therapy (zinc sulfate, 220 mg twice daily), low-dose androgen therapy (fluoxymesterone, 5-10 mg daily), and combination therapy (zinc sulfate and low-dose fluoxymesterone) on sperm motility and seminal zinc concentration in infertile patients with decreased motility and different zinc concentrations. They found that low-dose androgen therapy “increased seminal zinc concentrations and sperm motility, only when pretreatment seminal zinc concentrations were low. Furthermore, patients with low seminal zinc concentrations and poor sperm motility showed greater improvement of sperm motility and seminal zinc levels in response to zinc sulfate along with fluoxymesterone than they did to fluoxymesterone alone or zinc sulfate alone, possible due to a synergistic effect of zinc and androgen.”
These consistent but preliminary findings suggest that further research through well-designed and adequately powered clinical trials is warranted, with a focus on determining safety parameters and significators of pretreatment zinc status.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians treating patients with androgen therapy are advised to assess zinc status and coadminister a highly bioavailable zinc salt preparation (e.g., 55 mg elemental zinc twice daily) when indicated. Judicious standards of practice suggest monitoring for adverse effects of excessive zinc and coadministration of copper (1-3 mg daily, depending on baseline plasma or serum zinc/copper ratio).
Aminoglycoside antibiotics:Amikacin (Amikin), gentamicin (G-mycin, Garamycin, Jenamicin), kanamycin (Kantrex), neomycin (Mycifradin, Myciguent, Neo-Fradin, NeoTab, Nivemycin), netilmicin (Netromycin), paromomycin (monomycin; Humatin), streptomycin, tobramycin (AKTob, Nebcin, TOBI, TOBI Solution, TobraDex, Tobrex). Beta-lactam antibiotics:Methicillin (Staphcillin); aztreonam (Azactam injection); carbapenem antibiotics: meropenem (Merrem I.V.); combination drug: imipenem and cilastatin (Primaxin I.M., Primaxin I.V.); penicillin antibiotics: amoxicillin (Amoxicot, Amoxil, Moxilin, Trimox, Wymox); combination drug: amoxicillin and clavulanic acid (Augmentin, Augmentin XR, Clavulin); ampicillin (Amficot, Omnipen, Principen, Totacillin); combination drug: ampicillin and sulbactam (Unisyn); bacampicillin (Spectrobid), carbenicillin (Geocillin); cloxacillin (Cloxapen), dicloxacillin (Dynapen, Dycill), mezlocillin (Mezlin), nafcillin (Unipen), oxacillin (Bactocill), penicillin G (Bicillin C-R, Bicillin L-A, Pfizerpen, Truxcillin), penicillin V (Beepen-VK, Betapen-VK, Ledercillin VK, Pen-Vee K, Robicillin VK, Suspen, Truxcillin VK, V-Cillin K, Veetids), piperacillin (Pipracil); combination drug: piperacillin and tazobactam (Zosyn); ticarcillin (Ticar); combination drug: ticarcillin and clavulanate (Timentin). Cephalosporin antibiotics:Cefaclor (Ceclor), cefadroxil (Duricef), cefamandole (Mandol), cefazolin (Ancef, Kefzol), cefdinir (Omnicef), cefepime (Maxipime), cefixime (Suprax), cefoperazone (Cefobid), cefotaxime (Claforan), cefotetan (Cefotan), cefoxitin (Mefoxin), cefpodoxime (Vantin), cefprozil (Cefzil), ceftazidime (Ceptaz, Fortaz, Tazicef, Tazidime), ceftibuten (Cedax), ceftizoxime (Cefizox), ceftriaxone (Rocephin), cefuroxime (Ceftin, Kefurox, Zinacef), cephalexin (Keflex, Keftab), cephapirin (Cefadyl), cephradine (Anspor, Velocef); imipenem combination drug: imipenem and cilastatin (Primaxin I.M., Primaxin I.V.); loracarbef (Lorabid), meropenem (Merrem I.V.). Fluoroquinolone (4-quinolone) antibiotics:Cinoxacin (Cinobac, Pulvules), ciprofloxacin (Ciloxan, Cipro), enoxacin (Penetrex), gatifloxacin (Tequin), levofloxacin (Levaquin), lomefloxacin (Maxaquin), moxifloxacin (Avelox), nalidixic acid (Neggram), norfloxacin (Noroxin), ofloxacin (Floxin, Ocuflox), sparfloxacin (Zagam), trovafloxacin (alatrofloxacin; Trovan). Macrolide antibiotics:Azithromycin (Zithromax), clarithromycin (Biaxin), dirithromycin (Dynabac), erythromycin oral (EES, EryPed, Ery-Tab, PCE Dispertab, Pediazole), troleandomycin (Tao). Sulfonamide antibiotics:Sodium sulfacetamide (AK-Sulf, Bleph-10, Sodium Sulamyd), sulfamethoxazole (Gantanol), sulfanilamide (AVC), sulfasalazine (salazosulfapyridine, salicylazosulfapyridine, suphasalazine; Apo-Sulfasalazine, Azulfidine, Azulfidine EN-Tabs, PMS-Sulfasalazine, Salazopyrin, Salazopyrin EN-Tabs, SAS), sulfisoxazole (Gantrisin); combination drug: sulfamethoxazole and trimethoprim (cotrimoxazole, co-trimoxazole, SXT, TMP-SMX, TMP-sulfa; Bactrim, Bactrim DS, Cotrim, Septra, Septra DS, Sulfatrim, Uroplus); triple sulfa (Sultrin Triple Sulfa). Miscellaneous antibiotics:Bacitracin (Caci-IM), chloramphenicol (Chloromycetin), chlorhexidine (Peridex), clindamycin, oral (Cleocin); colistimethate (Coly-Mycin M), dapsone (DDS, diaminodiphenylsulphone; Aczone Gel, Avlosulfon), furazolidone (Furoxone), lincomycin (Lincocin), linezolid (Zyvox), nitrofurantoin (Macrobid, Macrodantin), trimethoprim (Proloprim, Trimpex), vancomycin (Vancocin). | Beneficial or Supportive Interaction, with Professional Management | | Bimodal or Variable Interaction, with Professional Management | | Potential or Theoretical Adverse Interaction of Uncertain Severity |
Probability:
2. Probable or 3. PossibleEvidence Base:
MixedEffect and Mechanism of Action
Administration of zinc may prevent or, in conjunction with standard oral antibiotic therapy and vitamin A, may enhance the acute treatment and accelerate recovery of infants and children with pneumonia. The role of zinc in immune function, generally by restoring immunocompetence and specifically as an acute-phase reactant, is presumed to provide the primary mechanism of action. However, such effect may occur only to the degree that nutrient coadministration corrects inadequate zinc intake or preexisting zinc deficiency.
During the “hot season,” concomitant zinc may delay recovery of some children and infants being treated for pneumonia with standard oral antibiotics. The mechanism of such a potential adverse effect has not been elucidated.
Research
The body of evidence on the effects of zinc in preventing and treating pneumonia, diarrhea, and other common diseases in malnourished infants and children is emerging and suggestive of a pattern of benefit but, as yet, mixed and incomplete. In a meta-analysis of randomized controlled trials, Bhutta et al. found that zinc supplementation in children in developing countries is associated with substantial reductions in the rates of pneumonia and diarrhea. In a randomized controlled trial involving 2482 children age 6 months to 3 years in an urban slum, Bhandari et al. found that zinc supplementation (with infants receiving 10 mg elemental zinc daily and older children 20 mg daily) “substantially reduced the incidence of pneumonia” in children who received single pharmacological dose of vitamin A (100,000 IU for infants and 200,000 IU for older children) at enrollment. In contrast, that same year (2002), in a double-blind, randomized controlled trial involving children age 9 months to 15 years in Calcutta, Mahalanabis et al. found that children with severe measles accompanied by pneumonia did not demonstrate any additional benefit, beyond that provided by antibiotics and vitamin A palmitate (100,000 IU dose), from coadministration of zinc acetate (containing 20 mg elemental zinc) twice daily for 6 days.
Subsequently, in a double-blind, placebo-controlled clinical trial involving 270 children age 2 to 23 months in a Bangladesh hospital, Brooks et al. compared the effects of concomitant elemental zinc (20 mg/day) versus placebo in combination with the hospital's standard antimicrobial management. Children in the zinc treatment group demonstrated reduced duration of severe pneumonia, including duration of chest indrawing, accelerated respiratory rate (>50 breaths/min), and hypoxia, and a shortened duration of overall hospitalization, with a mean reduction equivalent to one hospital day for both severe pneumonia and time in hospital. Less benefit was observed in children with wheezing. These researchers concluded that coadministration of “20 mg zinc per day accelerates recovery from severe pneumonia in children, and could help reduce antimicrobial resistance by decreasing multiple antibiotic exposures, and lessen complications and deaths where second line drugs are unavailable.” However, in a later, randomized, double-blind, placebo-controlled clinical trial involving 299 children, also age 2 to 23 months, being treated for severe pneumonia with standard antibiotic therapy in a hospital in southern India, Bose et al. reported a lack of therapeutic benefit from 10 mg zinc sulfate, versus placebo, twice a day during hospitalization. Specifically, they observed “no clinical or statistically significant differences in the duration of tachypnea, hypoxia, chest indrawing, inability to feed, lethargy, severe illness, or hospitalization.” Moreover, they reported “significantly longer duration of pneumonia in the hot season” in subjects treated with concomitant zinc.
The conflicting findings from this study compared with previous trials indicate that the value of zinc in preventing or correcting zinc deficiency may be the pivotal variable in the therapeutic response. Furthermore, the unexpected possibility of adverse effects, as seen in the “hot season” subgroup analysis, suggests the inadequacy of data underlying recommendations for routine administration of zinc in the treatment of pneumonia in young children in the developing world and the need for continued research with an emphasis on zinc-deficient populations.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians treating infants and children with pneumonia, or other severe acute lower respiratory infection, are advised to consider coadministration of zinc, and possibly vitamin A, with standard antibiotic therapy in patients demonstrating or at high risk for compromised zinc status. A dose of 10 mg elemental zinc twice daily is typical but can vary depending on the child's age and weight. Current scientific knowledge suggests that such doses are unlikely to produce any adverse effects during a short course of treatment, but limited data suggest greater caution in hot climates. Methods for determining zinc deficiency are generally considered unreliable, so patient history and clinical presentation are usually the best predictors of zinc deficiency. Health care professionals are also advised to educate parents to shift dietary intake patterns away from foods with a high phytate-to-zinc ratio in order to increase the bioavailability of dietary zinc. In general, zinc acetate provides the most bioavailable form of zinc, across a broad range of gastric pH. The potential for a pharmacokinetic interaction involving binding between zinc and the antibiotic agent suggests that separating oral intake by 2 to 4 hours would be prudent.
Erythromycin 3% and benzoyl peroxide 5% topical gel (Benzamycin). Clindamycin, topical (Cleocin T, Clindaderm). | Beneficial or Supportive Interaction, with Professional Management |
Probability:
2. ProbableEvidence Base:
PreliminaryEffect and Mechanism of Action
The important role of zinc in immune function and the health of the skin is well established. Zinc is effective in the treatment of inflammatory acne, and zinc salts have demonstrated bacteriostatic activity against Propionibacterium acnes. Zinc appears to exert a specific action on inflammatory cells, especially granulocytes, where the mechanism involved in zinc's “anti-inflammatory action is related to inhibition of polymorphonuclear leukocyte chemotaxis induced by a decreased granulocyte zinc level.”
Concomitant administration of zinc, oral and/or topical solution, may enhance the efficacy of topical antibiotics in the treatment of acne vulgaris.
Research
A limited but consistent body of evidence indicates that erythromycin-zinc combination therapy is effective in the treatment of acne. In a double-blind, randomized, multicenter study involving 122 patients with acne vulgaris, Habbema et al. evaluated the efficacy of a 4% erythromycin and zinc combination lotion (Zineryt) versus 2% erythromycin lotion (Eryderm). During visits at 0, 1, 2, 4, 8, and 12 weeks, they examined subjects and determined that treatment with erythromycin-zinc “combination lotion was more effective than with 2% erythromycin as regards the reduction in number of the acne lesions and the severity grade of the acne.” Subsequently, Schachner et al. conducted a 12-week double-blind trial to determine the safety and efficacy of a 4% erythromycin plus 1.2% zinc acetate formulation versus its vehicle. They continued the study for 40 weeks after the initial 12-week double-blind phase by switching vehicle-treated patients to active treatment and continuing to give patients treated with active drug the same treatment. Investigators reported “statistically significant differences” during the first 12 weeks “in the efficacy of the erythromycin-zinc compared with vehicle for acne severity grades (global assessment) and for papule, pustule, and comedo counts.” Moreover, following crossover, the subjects who had been receiving vehicle-only (placebo) treatment and then had been switched to active therapy duplicated the improvement of the first group treated with erythromycin-zinc. The authors reported “no clinical problems with superinfection or secondary infection” during 1 year of treatment in the 39 female patients (of the initial 73).
Dreno et al. also conducted in vivo and in vitro studies investigating the combination of topical erythromycin and oral zinc gluconate in the treatment of patients with inflammatory acne. In a trial involving 30 patients with inflammatory acne, they found that treatment with zinc gluconate (30 mg daily for 2 months) resulted in “a reduction in the number of inflammatory lesions after a 2-month treatment whether or not Propionibacterium acnescarriage was present,” as demonstrated in bacteriological samples taken at onset, day 30, and day 60. Further, they observed that in vitro “addition of zinc salts in the culture media of Propionibacterium acnesreduced resistance of Propionibacterium acnesstrains to erythromycin.” Thus, the authors concluded that the concomitant action of oral zinc salts acting systemically and topical erythromycin treatment “seems an interesting option in the light of an increasing number of patients carrying erythromycin resistant Propionibacterium acnesstrains.”
Nutritional Therapeutics, Clinical Concerns, and Adaptations
The scientific evidence, both broad and specific, indicates that health care professionals treating patients with acne, especially inflammatory acne, should consider integrating zinc into their therapeutic strategy. Whether by oral dose or combined in a topical preparation with an antibacterial agent, zinc can exert a beneficial effect directly and synergistically on the skin environment and broader immune function and on the pathological processes and pathogenic agents. A typical dose would be in the range of 20 to 40 mg elemental zinc per day orally and/or 1% to 2% topically. Continued zinc supplementation after cessation of antibiotics may be indicated in many patients as part of a comprehensive and individualized long-term strategy emphasizing dietary changes, hormonal modulation, and other interventions appropriate to the patient's characteristics and evolving needs. Patients who have a history of multiple courses of oral antibiotics will often also benefit from coadministration of probiotic bacterial flora over an extended period, at least in part through effects on digestive and immune function.
Evidence: Amitriptyline (Elavil), citalopram (Celexa), clomipramine (Anafranil), fluoxetine (Prozac, Sarafem). Extrapolated, based on similar properties: Tricyclic antidepressants:Amitriptyline combination drug: amitriptyline and perphenazine (Etrafon, Triavil, Triptazine); amoxapine (Asendin), desipramine (Norpramin, Pertofrane), doxepin (Adapin, Sinequan), imipramine (Janimine, Tofranil), nortriptyline (Aventyl, Pamelor), protriptyline (Vivactil), trimipramine (Surmontil). Selective serotonin reuptake inhibitor (SSRI) antidepressants:Escitalopram (S-citalopram; Lexapro), fluvoxamine (Faurin, Luvox), paroxetine (Atropax, Deroxat, Paxil, Seroxat), sertraline (Zoloft). | Beneficial or Supportive Interaction, with Professional Management |
Probability:
2. ProbableEvidence Base:
EmergingEffect and Mechanism of Action
Among its many functions, zinc is an important modulator of the CNS. In particular, hippocampal and cortical neurons, noted for high concentrations of zinc, “possess mechanisms for Zn 2+ uptake and storage in synaptic terminals” and for stimulation of release of Zn 2+ ions along with neurotransmitters. “Zn 2+ modulates predominantly the excitatory (glutamatergic) and inhibitory (GABA-ergic) amino acid neurotransmission pathways in CNS.” Thus, zinc deficiency impairs neurological function and is associated with depression.
Administration of zinc in patients diagnosed with depression may provide direct benefit and appears to enhance the effect of some conventional antidepressant medications, particularly those affecting monoamine transmitter reuptake or metabolism, at least in part by acting as a modulator of glutamatergic transmission. Chronic zinc administration, as well as most “clinically effective antidepressants,” induce expression of the gene coding for brain-derived neurotrophic factor (BDNF) and an increase in cortical (but not hippocampal) BDNF messenger RNA (mRNA) level; tranylcypromine, a classic antidepressant, increases BDNF mRNA level in both brain regions. Zinc administration also increases levels of synaptic pool zinc in the hippocampus. Moreover, changes in the brain, particularly a phenomenon known as “mossy fiber sprouting,” that occur with electroconvulsive shock (ECS), are associated with an increase in the synaptic zinc level in the hippocampus after such therapy and parallels effects of chronic but not acute zinc treatment. “Chronic treatment with citalopram (but not with imipramine or ECS) significantly (approx 20%) increased the serum zinc level. Chronic treatment with both drugs slightly (by approx 10%) increased the zinc level in the hippocampus and slightly decreased it in the cortex, cerebellum and basal forebrain.” Chronic imipramine treatment enhances the ability of zinc to inhibit the NMDA receptor complex in the cerebral cortex, but not in the hippocampus, but such effects appear to be species specific. Notably, chronic ECS may also induce a significant increase in zinc levels in the hippocampus (30%), as well as an 11% to 15% increase in zinc in other brain regions. Another mechanism of action may derive from zinc's “antagonistic action on group I metabotropic glutamate receptors or potentiation of AMPA receptors which both may attenuate the NMDA receptor function.” Zinc may also exert an antidepressant action through its direct inhibition of glycogen synthase kinase-3β, which has been proposed as a target for treatment of affective (bipolar) disorder. Thus, zinc acts as a natural modulator of amino-acidergic neurotransmission, particularly as an antagonist of the glutamate/ N-methyl- D-aspartate (NMDA) receptor, and zinc administration may correct derangements of zinc homeostasis so that its presence may be necessary for, and its coadministration may potentiate, the therapeutic effects of many conventional antidepressants.
Research
McLoughlin and Hodge initially published data reporting hypozincemia in patients with primary depressive disorders. Subsequently, one study by Maes et al. showed significantly lower serum zinc levels in individuals diagnosed with major depression, compared with nondepressed controls, and intermediate zinc levels in those with minor depression. In another study, however, these researchers found no correlation between these parameters among treatment-resistant patients. Further correlations have been observed between the serum level of zinc and the severity of illness in individuals with unipolar depression, as defined in the Hamilton Depression Rating Scale. The hypothesis that zinc status, as indicated by serum zinc concentrations, may be a sensitive and specific marker of depression is also supported by findings showing that lowered serum zinc concentrations may be normalized after successful antidepressant treatment.
In a series of in vitro and animal studies and human trials spanning nearly a decade, Polish researchers have investigated the function of zinc in relation to depression and the interactions between zinc and conventional antidepressants. They showed a similar “antidepressant-like performance” in mice and rats subjected to the forced-swim test, but also found differences in the effects of imipramine on locomotor function and in the responses of these two rodent species to chronic imipramine treatment that suggest the existence of species-dependent adaptive mechanisms involving zinc sites at the NMDA receptor complex. Further, a rodent model showed that the addition of low-dose zinc could potentiate the activity of antidepressants when administered at dosages too low to be effective and could synergistically achieve an antidepressant effect. In one innovative study, Nowak et al. demonstrated that the alteration in zinc interaction with NMDA receptors may be involved in psychopathology underlying suicidal attempts by showing a statistically significant (26%) reduction in the potency of zinc to inhibit NMDA receptor activity in the hippocampal, but not cortical, tissue of suicide subjects. Subsequently, these researchers conducted a placebo-controlled, double-blind pilot study investigating the efficacy of concomitant zinc (25 mg Zn 2+ ) and standard antidepressant pharmacotherapy using tricyclic antidepressants or SSRIs, specifically clomipramine, amitriptyline, citalopram, or fluoxetine, in the treatment of fourteen patients who fulfilled Diagnostic and Statistical Manual of Mental Disorders(4th edition, DSM-IV) criteria for major (unipolar) depression. Initially, after an initial washout period and throughout 12 weeks of treatment with antidepressant drugs and zinc or antidepressant drugs and placebo, they assessed therapeutic response to intervention using the Hamilton Depression Rating Scale and the Beck Depression Inventory. Subjects in both groups demonstrated an improvement in depressive symptoms at the second week, but the zinc-antidepressant group showed a statistically significant improvement in both measures, compared with the antidepressant-placebo group, at 6 and 12 weeks. The authors concluded that their findings, although preliminary, constituted “the first demonstration of the benefit of zinc supplementation in antidepressant therapy” and suggested that the effect “may be related to modulation of glutamatergic or immune systems by zinc ion.” Continued investigation of this interaction and its clinical implications is clearly warranted.
Greater refinement in methodology, to account for individual patient characteristics (e.g., clinical variation in condition, pharmacogenomics, personal history, lifestyle characteristics), will render future findings more robust and relevant to the dynamic and nuanced realities of treating the diverse presentations of depression. More broadly, further research, possibly framed within the more expansive model of psychoneuroimmunology, is warranted to investigate the potentially pivotal role of zinc in the interrelationships between the “immune system” and CNS function and thereby reveal the overarching unity of these supposedly discrete “systems” within human physiology and health, dysfunction and disease.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Health care professionals treating individuals diagnosed with depression, particularly physicians prescribing SSRI or tricyclic antidepressants, are advised to consider the potential value of zinc administration as part of a comprehensive, evolving, and individualized therapeutic strategy. The emerging body of scientific evidence strongly suggests that zinc may independently benefit many such patients, even outside compromised zinc status, and may enhance the efficacy of conventional antidepressant regimens, including pharmaceutical antidepressants and possibly electroconvulsive therapy. Pending further research, and the establishment of sensitive assays of zinc depletion, physiologic zinc administration, typically 25 to 40 mg elemental zinc daily, is generally considered safe and sufficient to achieve therapeutic effect. Coadministration of folic acid, DHEA, EPA (fish oil), inositol, or other synergistic nutritional support may also be efficacious with certain patients. Concomitant use of botanical medications, such as Hypericum perforatum(St. John's wort), Ginkgo biloba, Rhodiola rosea, Withania somnifera(Ashwaganda), is controversial and may be useful but requires assessment, prescribing, and management by a health care professional trained and experienced in botanical therapeutics, in coordination with the physician prescribing any pharmacotherapy.
See Calcium in Nutrient-Nutrient Interactions.
Evidence: Captopril (Capoten), enalapril (Vasotec). Extrapolated, based on similar properties: Benazepril (Lotensin); combination drug: benazepril and amlodipine (Lotrel); captopril combination drug: captopril and hydrochlorothiazide (Acezide, Capto-Co, Captozide, Co-Zidocapt); cilazapril (Inhibace); enalapril combination drugs: enalapril and felodipine (Lexxel); enalapril and hydrochlorothiazide (Vaseretic); fosinopril (Monopril), lisinopril (Prinivil, Zestril); lisinopril and hydrochlorothiazide (Prinzide, Zestoretic); moexipril (Univasc), perindopril (Aceon), quinapril (Accupril), ramipril (Altace), trandolapril (Mavik). | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, with Professional Management | | Prevention or Reduction of Drug Adverse Effect |
Probability:
2. ProbableEvidence Base:
ConsensusEffect and Mechanism of Action
The ACE inhibitors possess a prominent zinc-binding moiety that binds to zinc ions in the active site of the ACE molecule. Drugs within the class of ACE inhibitors can be classified according to the ligand of the zinc ion of ACE and according to the excretion route of their active moiety. Thus, captopril has a sulfhydryl moiety as the zinc-binding ligand, whereas enalapril has a carboxyalkyl dipeptide moiety. Both captopril and enalapril are excreted primarily through the kidneys, but enalapril has a much longer duration of action than captopril. Gradual zinc depletion occurs as zinc is bound to the ACE inhibitor and can lead to zinc insufficiency. Some of the adverse effects associated with ACE inhibitors, such as hypogeusia, coincide with known characteristics of zinc depletion and may derive, at least in part, from the effect of these agents on zinc status.
Research
Several studies have demonstrated that captopril (and, at a slower pace, enalapril) is likely to cause significant urinary zinc loss, which over several months can lead to zinc depletion with attendant decreased red blood cell (RBC) zinc concentrations and reduced taste acuity (hypogeusia), even in the absence of adverse changes in serum zinc levels. In 1987, O’Connor et al. reported that serum zinc was unaffected by captopril treatment of hypertension. However, the next year, Abu-Hamdan et al. documented changes in taste acuity and zinc metabolism in a trial involving 31 hypertensive male patients treated with captopril. In comparing 11 long-term, high-dose captopril recipients (>6 months, 266 mg/day), six short-term captopril recipients (<6 months, 104 mg/day), and 14 noncaptopril controls, they found that, compared to controls, the long-term captopril group had significantly higher taste detection and recognition thresholds, lower plasma zinc, and higher urinary zinc excretion. The short-term captopril group did not differ significantly from the noncaptopril group, except for altered taste-recognition thresholds. Notably, two long-term captopril patients reported improved taste acuity and demonstrated “almost normalized zinc parameters” after discontinuing captopril.
Subsequently, Golik et al. conducted two trials comparing the effects of captopril and enalapril on zinc metabolism in hypertensive patients. First, in a small retrospective study, they assessed several parameters of zinc metabolism in 13 patients with essential hypertension, of whom six were chronically taking captopril, seven were taking enalapril, and six were untreated, as well as nine healthy controls. Although serum zinc levels were comparable in all groups, the captopril-treated subjects exhibited significantly increased 24-hour urinary zinc excretion compared with the three other groups. Further, subjects in both the captopril and the enalapril group exhibited a significant increase in the zinc/creatinine ratio in 24-hour urine, which was significantly greater in the captopril group. Notably, even though plasma zinc concentrations were comparable in all groups, subjects in the captopril group demonstrated significantly decreased RBC zinc values compared with those in the three other groups. The authors concluded that “(1) although both captopril and enalapril produce renal zinc loss, this loss is far greater in patients receiving captopril; and (2) captopril administration over 3 months or more generates RBC zinc depletion.” Several years later, in a prospective trial involving 44 subjects, these researchers investigated the effects of chronic captopril and enalapril treatment on zinc metabolism in hypertensive patients. They measured and compared zinc levels in serum, 24-hour urine samples, and peripheral blood monocytes at baseline and after 6 months in 10 patients newly diagnosed with essential hypertension who were randomly divided for ACE therapy, with 16 receiving captopril only and 18 receiving enalapril only, as well as 10 healthy subjects serving as controls. They found that patients in the captopril- and enalapril-treated groups demonstrated significantly decreased intramonocytic zinc levels over the same period, but that only subjects in the captopril-treated group showed a significant enhancement of 24-hour urinary zinc excretion after 6 months of treatment. Thus, the authors concluded: “Treatment of hypertensive patients with captopril or enalapril may result in zinc deficiency.”
Subsequently, Peczkowska confirmed that ACE inhibitor therapy may adversely affect zinc metabolism. Although not statistically significant, serum zinc decreased more significantly in a group treated with captopril after 8 weeks of therapy than in a group receiving benazepril. Collectively, these findings indicate that captopril can cause clinically significant zinc depletion over several months, which may not be detectable through serum zinc assay. Other ACE inhibitors probably have a similar effect on zinc metabolism, although zinc depletion at the tissue level apparently occurs at a slower rate and possibly to a lesser degree.
In related research, Golik et al. also determined that individuals with type 2 diabetes mellitus and congestive heart failure “excrete larger amounts of zinc, which may eventually lead to zinc deficiency.” These findings bear directly on the data relating to hypertensive medications, given the widespread use of ACE inhibitors for heart failure and the high incidence of hypertension among these patient populations.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians prescribing captopril or other ACE inhibitors are advised to discuss supportive coadministration of zinc (50 mg elemental zinc twice daily) to counter probable nutrient depletion. The risk attendant to such supplementation is minimal and its characteristics well known. Establishing zinc depletion through laboratory assessment is not considered sensitive enough to be clinically reliable because of the limitations of testing methods in the face of metabolic flux characteristic of zinc physiology. Clinical signs of zinc deficiency are more reliable but tend to manifest only with advanced deficiency, usually after subclinical depletion has adversely affected function. Patients who develop ACE inhibitor–associated cough, frequently cited as a cause of nonadherence, may also experience amelioration with iron supplementation. Concomitant synergistic minerals (e.g., magnesium) as well coenzyme Q10 and hawthorn (Crataegus)could potentially further enhance therapeutic outcomes in the treatment of hypertension, heart failure, and related cardiovascular disease. Copper is generally advisable to balance the potential depletion by zinc. However, to avoid absorption problems inhibiting bioavailability of both ACE inhibitors and zinc (as well as other nutrients), patients should wait at least 2 hours after administration of the medication before taking any supplements.
Supplementation of any minerals by patients with renal failure or on dialysis can be dangerous and should only be done within the context of close medical supervision. Patients receiving ACE inhibitor therapy may experience an exaggeration of adverse effects often associated with intravenous administration of iron salts; monitor closely for adverse effects such as nausea, vomiting, and hypotension. Notably, potassium is usually contraindicated with ACE inhibitors because they greatly decrease renal potassium excretion.
Chlorhexidine (Chlorohex, Corsodyl, Eludril, Oro-Clense, Peridex, Periogard Oral Rinse). Similar properties but evidence indicating no or reduced interaction effects: Periochip. | Prevention or Reduction of Drug Adverse Effect | | Beneficial or Supportive Interaction, with Professional Management |
Probability:
2. ProbableEvidence Base:
PreliminaryEffect and Mechanism of Action
Chlorhexidine is known to cause staining of teeth when used as a rinse in dental care. The combination of zinc or other metal ions in solution with chlorhexidine can reduce the severity of such staining and enhance the plaque-inhibiting effect of the treatment. Zinc and other metal ions, such as tin (usually in the form of stannous fluoride), have the same receptor sites as chlorhexidine in the oral cavity, such that binding affinity for chlorhexidine is greater when the ions were applied together.
Research
The research into this interaction is preliminary in nature and limited in scope but consistent in its findings and their rationale. Waler and Rolla investigated the plaque-inhibiting effect of chlorhexidine in combination with zinc (and tin) in a group of students. They observed that “chlorhexidine and zinc (0.2% and 0.3% respectively) gave a plaque inhibiting effect slightly better than chlorhexidine alone” and superior to pre-rinses with metal ions or chlorhexidine first and metal ions afterward. They concluded that “the metal ions and chlorhexidine have the same receptor sites in the oral cavity, chlorhexidine exhibiting the stronger affinity when the ions were applied together.”
Subsequently, in a 6-month, randomized, stratified double-blind parallel study with 208 participants, Sanz et al. investigated the effect of a dentifrice containing chlorhexidine and zinc on plaque, gingivitis, calculus, and tooth staining. Of the three test groups, the two receiving chlorhexidine as part of their treatment (with or without zinc) exhibited “significant reductions in plaque and gingivitis (gingival index and number of bleeding sites)… compared with the control group,” but tooth staining was also higher. The group treated with the chlorhexidine-zinc rinse exhibited “significantly less staining compared with the positive control.” These authors concluded that the chlorhexidine-zinc dentifrice “will contribute to a significant improvement in oral hygiene with less staining compared with using a 0.12% chlorhexidine rinse.” Further clinical trials are warranted given the positive findings of these preliminary studies. The stability and acidic nature of these formulations in clinical practice are among the potential concerns deserving attention.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Dental professionals administering chlorhexidine are advised to consider adding zinc, usually as zinc sulfate heptahydrate, to their chlorhexidine preparation. No significant adverse effects, other than the probable bad taste, are to be expected. Direct evidence is lacking to confirm the efficacy of oral zinc administration alone in achieving similar preventive effects. Perhaps more importantly, clinicians should educate patients that brushing before applying the dentifrice is the most effective way to reduce chlorhexidine staining, because chlorhexidine adheres to plaque. Likewise, cultivating a healthy oral environment, by reducing acidity and supporting healthy oral flora, is also essential to preventing caries and erosion.
Evidence: Ciprofloxacin (Ciloxan, Cipro), norfloxacin (Noroxin); 8-hydroxyquinoline. Extrapolated, based on similar properties: Cinoxacin (Cinobac, Pulvules), enoxacin (Penetrex), gatifloxacin (Tequin), levofloxacin (Levaquin), lomefloxacin (Maxaquin), moxifloxacin (Avelox), nalidixic acid (Neggram), ofloxacin (Floxin, Ocuflox), sparfloxacin (Zagam), trovafloxacin (alatrofloxacin; Trovan). | Minimal to Mild Adverse Interaction—Vigilance Necessary | | Impaired Drug Absorption and Bioavailability, Precautions Appropriate | | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, Not Requiring Professional Management | | Prevention or Reduction of Drug Adverse Effect |
Probability:
1. Certain or 2. Probable (depending on agent and timing)Evidence Base:
Consensus but PreliminaryEffect and Mechanism of Action
Zinc salts and the 3-carbonyl and 4-oxo functional groups on quinolone antibiotics can bind within the gastrointestinal (GI) tract to form a poorly absorbed, stable chelation complex. This binding process, which may not be limited to the gut, can interfere to varying degrees with the absorption, bioavailability, and activity of both the antimicrobials in this class and the orally administered preparations containing zinc.
In one permutation of this interaction with a related quinolone, coadministration of zinc oxide may form chelates that inhibit the antibacterial activity or even counteract the antimycotic activity of 8-hydroxyquinoline, but may also mitigate allergic reactions to the 8-hydroxyquinoline.
Research and Reports
In vitro experiments first demonstrated the pattern of interaction between quinolones and metals in an aqueous medium and the resultant effects on antimicrobial activity. Subsequently, changes in oral bioavailability and alterations in therapeutic efficacy have been the focus of many previous interaction studies involving metal cations and quinolones. Thus, through multiple lines of research, the ability of multivalent cations to reduce the absorption and serum levels of oral quinolone antibiotics is generally considered well established.
Evidence from clinical trials focusing on zinc-quinolone interactions is limited. Most of the evidence used to predict direct, one-to-one interactions between zinc and various quinolone agents is extrapolated from findings based on research involving iron and based on similar chemistry and presumed mechanisms of action. Similarly, calcium, magnesium, manganese, and copper, as well as milk and calcium-fortified juices, inhibit absorption of fluoroquinolones. Much of the remaining data derive from studies using multimineral preparations, usually with iron the primary interacting agent. The situation with case reports is similar. In a four-way crossover trial with 12 healthy volunteers, Polk et al. (1989) observed a clinically significant reduction in the absorption of orally administered doses of ciprofloxacin (500 mg) when administered with a multivitamin-mineral formulation containing zinc, or ferrous sulfate (325 mg orally three times daily). Notably, peak concentrations of ciprofloxacin with ferrous sulfate regimen were below the minimum inhibitory concentration (MIC) for 90% of strains of many organisms normally considered susceptible to the antimicrobial activity of ciprofloxacin. Kara et al. investigated clinical and chemical interactions between ciprofloxacin and iron preparations and found impairment of absorption with a multimineral preparation containing iron, magnesium, zinc, calcium, copper, and manganese (Centrum Forte). In an experiment involving eight healthy volunteers, each receiving a different metal ion, Campbell et al. found that zinc sulfate reduced the urinary recovery of norfloxacin by 56%, just slightly more than ferrous sulfate. In reviewing the available data, Stockley concluded: “There seems to be very little data about the zinc/quinolone interaction, but zinc appears to interact like iron so that the same precautions suggested for iron should be followed.”
The particular interaction between zinc oxide and 8-hydroxyquinoline, a related quinoline, is more nuanced, although the data are rather limited. In a case report and subsequent trial involving 13 patients, Fischer found that zinc oxide in a base reduced the eczematogenic effects associated with 8-hydroxyquinoline compared with an ointment using a paraffin base without zinc. However, this combination also inhibited the antibacterial and antimycotic activity of the medication and appeared to promote the growth of Candida albicans. Consequently, this interaction, particularly chelate formation, can interfere with the therapeutic effects of the 8-hydroxyquinoline to the degree that substantially “little or no antibacterial properties” remain.
Zinc depletion resulting from chelation by this class of medications has not been studied per se. Although plausible, such an adverse effect on zinc status is highly improbable given the limited duration of standard fluoroquinolone antibiotic use. Long-term quinolone therapy and simultaneous oral zinc intake in the face of zinc deficiency could theoretically contribute to lack of tissue repletion. It is unclear whether long-term oral fluoroquinolone antibiotic therapy might cause clinically significant zinc depletion in certain vulnerable populations by preventing dietary zinc absorption.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
The reduction of fluoroquinolone activity by simultaneously ingested zinc salts is a widely accepted, although not necessarily well-documented, interaction between these two groups of agents; the potential depletion of zinc through the same mechanisms is plausible but generally improbable in standard clinical use. Both directions of interaction and decreased bioavailability can be adequately avoided through proper patient education and dose timing. Notably, even with iron, the degree of interaction effect depends greatly on the particular quinolone agent involved, as well as timing of oral intake(s). Inherently, such separation of intake is irrelevant with combined topical formulations, and evidence indicates that the effectiveness of topical quinolone preparations may be compromised by the addition of zinc.
Patients with acute infections, diagnosed or presumed, frequently self-administer zinc because of its immune-supporting activity and often fail to inform their health care professionals. Physicians treating patients for serious infections with quinolone antibiotics should advise that they refrain from ingesting zinc supplements, or using multivitamin-mineral formulations containing zinc or other divalent mineral cations, during the course of therapy to avoid interfering with the absorption and thus the antimicrobial action of the medication.
Zinc intake can usually be temporarily halted in most patients but can be continued with separation of intake timing in those for whom concomitant zinc supplementation has been confirmed as necessary to other therapeutic needs. If this is not possible, administration of the medication 2 hours before or 6 hours after ingestion of an oral zinc or multimineral supplement is suggested and can effectively minimize risk of an adverse interaction (i.e., antibiotic malabsorption). This recommendation may also apply to intake of zinc-rich or zinc-fortified foods. Monitor for decreased therapeutic effects of oral quinolones if inadvertently administered simultaneously with oral zinc or multimineral supplements.
Evidence: Clobetasol (clobetasol topical; Cormax, Dermoval, Dermotyl, Dermovate, Dermoxin, Eumosone, Lobate, Olux, Temovate, Temovate E, Topifort). Related, no evidence for extrapolation: Alclometasone (Aclovate, Modrasone), amcinonide (Cyclocort), beclomethasone, betamethasone dipropionate/valerate (betamethasone topical; Alphatrex, Beta-Val, Betaderm, Betanate, Betatrex, Diprolene AF, Diprolene, Diprosone, Luxiq, Maxivate, Teladar, Uticort, Valisone), clobetasone (Eumovate), clocortolone (clocortolone pivalate topical; Cloderm), desonide (DesOwen, Tridesilon), desoximetasone (Topicort, Topicort LP), desoxymethasone, dexamethasone (Aeroseb-Dex, Decaderm, Decadron, Decaspray), diflorasone (Apexicon, Florone, Maxiflor, Psorcon), diflucortolone (Nerisona, Nerisone), fluocinolone (Derma-Smoothe/FS, Fluonid, Synelar, Synemol), fluocinonide (Fluonex, Lidex, Lidex-E, Lonide, Vanos), fludroxycortide (flurandrenolone), fluocortolone (Ultralan), flurandrenolide (Cordran, Drenison), fluticasone (Cutivate), halcinonide (Halog), halobetasol (Ultravate); hydrocortisone 17-butyrate/acetate/probutate/valerate (hydrocortisone topical; Acticort100, Aeroseb-HC, Ala-Cort, Ala-Scalp HP, Allercort, Alphaderm, Bactine, Beta-HC, Caldecort Anti-Itch, Cetacort, Cort-Dome, Cortaid, Cortef, Cortifair, Cortizone, Cortone, Cortril, Delacort, Dermacort, Dermarest, DriCort, DermiCort, Dermtex HC, Epifoam, Gly-Cort, Hi-Cor, Hydro-Tex, Hytone, LactiCare-HC, Lanacort, Lemoderm, Locoid, MyCort, Nutracort, Pandel, Penecort, Pentacort, Proctocort, Rederm, S-T Cort, Synacort, Texacort, Westcort); mometasone (Elocon, mometasone topical), triamcinolone (Aristocort, Triderm, Kenalog, Flutex, Kenonel, triamcinolone topical); triamcinolone and nystatin (Mycolog II). | Beneficial or Supportive Interaction, with Professional Management |
Probability:
3. PossibleEvidence Base:
PreliminaryEffect and Mechanism of Action
Clobetasol is a synthetic glucocorticoid derived from cortisol. Possessing significant corticosteroid activity and minor mineralocorticoid activity, it is used clinically for its activity as a topical anti-inflammatory and immunosuppressant, particularly for corticosteroid-responsive dermatoses, and systemically in replacement therapy for adrenal insufficiency. Zinc has demonstrated beneficial effects in supporting healthy skin and immune function generally, and facilitating tissue repair in particular, as does biotin, with which it can be combined. Coadministration of zinc and topical clobetasol, along with other synergistic nutrients such as biotin, may provide for enhanced therapeutic effect in the treatment of inflammatory dermatological conditions.
Research
Limited research suggests a potential synergistic effect may be obtained from combining zinc and clobetasol, especially as part of a more comprehensive therapeutic strategy. In a published letter, Camacho and Garcia-Hernandez reported that children with alopecia areata exhibited greater improvement when administered a treatment combining topical clobetasol with zinc aspartate (100 mg daily) and biotin (20 mg daily) than did children treated with oral corticosteroids. These findings are promising but primarily serve to indicate that further research is warranted.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians treating inflammatory dermatological conditions such as alopecia areata with clobetasol or related topical corticosteroids may find that the addition of zinc, especially with other synergistic nutrients such as biotin, may enhance the therapeutic efficacy of the intervention. Patients should be advised of the preliminary nature of the scientific evidence, but also of the underlying rationale of the combination and the relatively low additional risk. In particular, such an approach may provide greater benefit and lesser adverse effects than oral corticosteroids.
Cisplatin ( cis-Diaminedichloroplatinum, CDDP; Platinol, Platinol-AQ).
See EDTA in Theoretical, Speculative, and Preliminary Interactions Research.
Betamethasone (Celestone), cortisone (Cortone), dexamethasone (Decadron), fludrocortisone (Florinef), hydrocortisone (Cortef), methylprednisolone (Medrol) prednisolone (Delta-Cortef, Orapred, Pediapred, Prelone), prednisone (Deltasone, Liquid Pred, Meticorten, Orasone), triamcinolone (Aristocort). See also Clobetasol and Related Topical Corticosteroids. | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, with Professional Management | | Potential or Theoretical Adverse Interaction of Uncertain Severity |
Probability:
3. PossibleEvidence Base:
Emerging or ConsensusEffect and Mechanism of Action
Zinc modulates acute immune response and promotes normal tissue repair. The adenohypophyseal-adrenocortical network plays a critical role in maintaining circulating zinc and in mobilizing zinc stores from tissue stores. Under adrenocorticotropic hormone (ACTH) stress, the reaction of cortisol release is physiological, whereas the serum zinc level decreases significantly. Thus, zinc metabolism can be significantly affected by both internal processes such as inflammation and exogenous influences such as glucocorticoid administration.
Oral corticosteroid medications, particularly at high doses, can cause increased urinary excretion of zinc and reduced serum zinc levels; significant effect is less probable with short-term, low-level corticosteroid administration. Effects also vary through the course of steroid administration.
Zinc has been said to impair or interfere with the activity of corticosteroids or other immunosuppressant drug regimens because of its “immunostimulant” activity. No specific mechanism of action or other scientific data have been provided to support such assertions. This oversimplification likely derives from a misunderstanding of zinc's role in the immune system. Zinc deficiency is a documented cause of immune dysfunction, and zinc repletion restores normal immune function; however, zinc has not been demonstrated to act as an immune “stimulant.”
Research
The scientific data on the interaction between corticosteroids and zinc have evolved over 30 years but still provide an incomplete understanding of the mechanisms involved and their clinical implications, especially with regard to the stages of immune response, tissue repair, and the role of the pituitary/adrenal axis in zinc metabolism. In 1971, Briggs et al. reported that short-term, low-level prednisolone (5 or 10 mg/day) did not significantly effect serum zinc concentrations. That same year, Flynn et al. published their findings on the effects on zinc during use of corticosteroids as vasodilators in the treatment of low-cardiac-output syndrome (LCOS) in patients with major burns (with or without LCOS) and surgical patients (with LCOS) compared with 30 elective or emergency surgery patients acting as controls. They noted that earlier researchers had found that elevated “serum and urine corticosteroids and, eventually, adrenocortical exhaustion have been reported in the early stages in severe burns,” and that serum zinc “is also raised during the first day after the burn and starts to decrease rapidly after the seventh day.” Intravenous (IV) corticosteroids were administered in pharmacological doses to the major burn patients with LCOS (hydrocortisone, 800 mg every 6 hours) and in a vascular-surgery patient with LCOS (dexamethasone phosphate, 200 mg, equivalent to 8.0 g cortisone). They observed that “massive doses of steroids rapidly lower serum-zinc levels” in seriously ill burn patients and differentiated that response from the response to low-dose steroids as reported by Briggs. “The extent of pituitary/adrenal shutdown is likely to play a vital role in the differences between high and low dose effects.” Both controls who underwent surgery and “major burn and L.C.O.S. patients receiving non-steroid therapy had similar zinc patterns (i.e., increased zinc with the stress during the first days after injury or onset of L.C.O.S.).” However, only patients who received large doses of steroids exhibited rapid zinc loss. “Falls of 30-75 mcg per 100 ml were recorded as little as 1 hour after a single bolus of corticosteroids.” Based on these and other findings, the authors concluded that the “actions of large doses of corticosteroids in major burn and L.C.O.S. patients point to a role for the adenohypophyseal/adrenocortical system in maintaining circulating zinc levels…. Increases and decreases in serum-zinc are linked to stress-induced activation and steroid-produced deactivation of the pituitary/adrenal axis” and as such indicate a central role of the pituitary/adrenal axis in regulating serum zinc changes and mobilizing body zinc stores. Subsequent research by Fodor et al. confirmed “that the zinc metabolism probably depends on glucocorticoidal controls.”
Likewise, Yunice et al. conducted an experiment comparing the effects of varying doses of a short-acting (methylprednisolone) and a long-acting (dexamethasone) synthetic glucocorticoid on extent and duration of alterations in plasma zinc and copper concentrations in normal humans. They observed increases in plasma zinc (and copper) levels shortly after IV administration of either steroid. However, plasma zinc concentrations decreased below control levels by 12 hours, and no significant decrease was noted beyond 48 hours; “the extent and duration of the depression depended on the dosage of the steroid administered.” The authors concluded that their findings suggested “serum zinc levels may depend on ACTH-adrenal interactions.”
In related research, Fell et al. tracked zinc mobilization in two patients after hip replacement surgery and correlated it with muscle catabolism. They measured large increases in the daily excretion of zinc-65 ( Zn), total zinc, and nitrogen, with the maximum excretion occurring about 10 days after surgery and observed a “good correlation between the increased excretion of Zn and total zinc, indicating the tissue origin of the latter as skeletal muscle.” Because Zn is a radioactive form used only in research, these findings offer data more toward developing physiological knowledge than directly applicable to clinical monitoring of normal Zn.
More broadly, research investigating the connections between endogenous steroid regulation and zinc metabolism might reveal valuable insights into the possible role of zinc status in the adverse effects of elevated cortisol, steroid release, and other components of stress response physiology that adversely affect immune function.
No evidence from clinical trials or qualified case reports substantiates broad assertions that zinc should not be administered concomitantly with corticosteroids or other immunosuppressant drug regimens because of its “immunostimulant” activity. Further research would be warranted should preliminary findings strongly indicate the occurrence of such a phenomenon.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians prescribing oral corticosteroids are advised to consider the potential benefit of coadministering zinc as a therapeutic synergist and, in patients taking long-term steroids, for prevention of depletion. The available evidence indicates that zinc plays an important role in physiological response to trauma and participates in immune and tissue repair functions, as in cases involving severe burns. Moreover, both acute and chronic use of steroids can contribute to zinc depletion patterns. In some cases, depletion is more probable with administration for longer than 2 weeks. In other situations, however, acute depletion, especially in the context of injuries or pathologies putting high demands on physiological zinc metabolism, acute high-dose steroids may cause zinc depletion with greater potential for clinically significant adverse effects.
A daily dose of 15 to 50 mg elemental zinc per day, within the context of appropriate supervision, will generally facilitate healing and prevent depletion without introducing substantial risk of significant adverse effects. Although serum zinc was used for assessment in some relevant research, expert consensus agrees that no sensitive laboratory method exists for detecting zinc depletion in tissue stores and zinc pools. The theoretical concern that zinc might counteract intentional immunosuppressant activity lacks substantive evidence-based support and, even if true, might be beneficial in some cases and only potentially detrimental in others, depending on the condition being treated, patient characteristics, therapeutic strategy, and phase of treatment intervention. Further research through well-designed and adequately powered trials is warranted to determine safety and efficacy, mechanisms, indications, and treatment guidelines.
Oral Contraceptives: Monophasic, Biphasic, and Triphasic Estrogen Preparations (Synthetic Estrogen and Progesterone Analogs):
Ethinyl estradiol and desogestrel (Desogen, Ortho-TriCyclen).Ethinyl estradiol and ethynodiol (Demulen 1/35, Demulen 1/50, Nelulen 1/25, Nelulen 1/50, Zovia).Ethinyl estradiol and levonorgestrel (Alesse, Levlen, Levlite, Levora 0.15/30, Nordette, Tri-Levlen, Triphasil, Trivora).Ethinyl estradiol and norethindrone/norethisterone (Brevicon, Estrostep, Genora 1/35, GenCept 1/35, Jenest-28, Loestrin 1.5/30, Loestrin1/20, Modicon, Necon 1/25, Necon 10/11, Necon 0.5/30, Necon 1/50, Nelova 1/35, Nelova 10/11, Norinyl 1/35, Norlestin 1/50, Ortho Novum 1/35, Ortho Novum 10/11, Ortho Novum 7/7/7, Ovcon-35, Ovcon-50, Tri-Norinyl, Trinovum).Ethinyl estradiol and norgestrel (Lo/Ovral, Ovral).Etonogestrel/ethinyl estradiol vaginal ring (Nuvaring).Mestranol and norethindrone (Genora 1/50, Nelova 1/50, Norethin 1/50, Ortho-Novum 1/50).Related, internal application: Etonogestrel/ethinyl estradiol vaginal ring (Nuvaring).Hormone Replacement Therapy (HRT), Estrogens
Chlorotrianisene (Tace); conjugated equine estrogens (Premarin); conjugated synthetic estrogens (Cenestin); dienestrol (Ortho Dienestrol); esterified estrogens (Estratab, Menest, Neo-Estrone); estradiol, topical/transdermal/ring (Alora Transdermal, Climara Transdermal, Estrace, Estradot, Estring FemPatch, Vivelle-Dot, Vivelle Transdermal); estradiol cypionate (Dep-Gynogen, Depo-Estradiol, Depogen, Dura-Estrin, Estra-D, Estro-Cyp, Estroject-LA, Estronol-LA); estradiol hemihydrate (Estreva, Vagifem); estradiol valerate (Delestrogen, Estra-L 40, Gynogen L.A. 20, Progynova, Valergen 20); estrone (Aquest, Estragyn 5, Estro-A, Estrone ‘5’, Kestrone-5); estropipate (Ogen, Ortho-Est); ethinyl estradiol (Estinyl, Gynodiol, Lynoral).Medroxyprogesterone-containing HRT and contraceptives: Medroxyprogesterone, oral (Cycrin, Provera); conjugated equine estrogens and medroxyprogesterone (Premelle cycle 5, Prempro).Progestin/Progestogen-Only Oral Contraceptives, Implants, and Postcoital Contraceptives
Related, evidence lacking for extrapolation: Etonogestrel, implant (Implanon); levonorgestrel, implant (Jadelle, Norplant; Norplant-2); levonorgestrel, oral postcoital contraceptive (Duofem, Escapelle, Levonelle, Levonelle-2, Microlut, Microval, Norgeston, NorLevo, Plan B, Postinor-2, Vika, Vikela); medroxyprogesterone, injection (depot medroxyprogesterone acetate, DMPA; Depo-Provera, Depo-subQ Provera 104); NES progestin, implant (ST-1435, Nestorone); norgestrel, oral (Ovrette).Hormone Replacement Therapy
Related, evidence lacking for extrapolation:Estrogen/progestin combinations:Conjugated equine estrogens and norgestrel (Prempak-C); estradiol and dydrogesterone (Femoston); estradiol and norethindrone, patch (CombiPatch); estradiol and norethindrone/norethisterone, oral (Activella, Climagest, Climesse, FemHRT, Trisequens); estradiol valerate and cyproterone acetate (Climens); estradiol valerate and norgestrel (Progyluton); estradiol and norgestimate (Ortho-Prefest).Estrogen/testosterone combinations:Esterified estrogens and methyltestosterone (Estratest, Estratest HS).See also Androgens. | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, Not Requiring Professional Management | | Beneficial or Supportive Interaction, with Professional Management |
Probability:
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XXXEffect and Mechanism of Action
The use of oral contraceptives (OCs) may be associated with decreased serum levels of zinc. Conversely, conjugated estrogens and medroxyprogesterone may reduce previously elevated urinary zinc excretion (as well as magnesium) in osteoporotic postmenopausal women. No specific mechanisms have been established to explain the various observed interactions phenomena, singly or collectively.
Research
The effects of exogenous estrogens on zinc levels can vary depending on the form and dose of estrogen administered, concomitant agents in formulation, patient characteristics (including life stage), and therapeutic intent. A significant incidence of zinc deficiency has been documented in females of all ages in a broad range of socioeconomic conditions, with the greatest risk in premature infants; low-income urban infants, children, adolescents, and women of childbearing age; and populations with a high-cereal diet.
Dorea et al. assessed serum levels of zinc and copper in 44 women of the same age group, 24 of whom were taking OCs and 20 serving as controls. They observed that “serum zinc was significantly lower while serum copper was significantly higher for women taking the oral contraceptive agents,” but that there was “no significant correlation between the serum zinc and copper levels” in either group. In general, adolescents in the United States tend to have inadequate intake of zinc and other micronutrients, with dietary intakes of zinc less than 75% of the U.S. RDA in more than one-third and less than 50% using nutritional supplements.
In a trial involving 37 postmenopausal women, some of whom exhibited signs of osteoporosis, Herzberg et al. compared serum and urinary zinc levels before and after 6 and 12 months of treatment with estrogen replacement therapy (ERT) consisting of conjugated estrogens (0.625 mg) and medroxyprogesterone acetate (5 mg). They observed a “consistent negative association … between changes in bone mineral density and urinary zinc excretion in the osteoporosis group” and an association between ERT and “reduced excretion of zinc, magnesium, and hydroxyproline in the elevated zinc excretion group.” In particular, urinary zinc excretion decreased 35% after 3 months and 26% after 1 year of ERT. In contrast, serum levels of zinc (as well as magnesium, calcium, and phosphate, but not alkaline phosphatase) “showed only negligible changes during ERT.” Noting this significant decrease in urinary zinc excretion after 3 months of ERT, the authors concluded that this “change was more pronounced in women with osteoporosis and elevated zinc excretion” and was associated with changes in bone metabolism rather than variation in diet.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians prescribing exogenous estrogen preparations may consider the potential value of coadministering zinc, with the effect and rationale varying for different populations using estrogen for different purposes. In women using OCs, coadministration of a multimineral/multivitamin formulation containing zinc, as well as vitamin B 6 and folic acid, may reduce adverse effects of the medication, including nutrient depletion. The probability that such nutritional support will be beneficial is generally greater in patients with compromised nutritional intake. Women treated with ERT may derive benefit against osteoporotic tendencies with concomitant zinc, particularly if they have compromised nutrient intake and signs if osteoporosis. The use of concomitant zinc at a physiologic dosage level, 15 to 40 mg elemental zinc daily, is generally safe and unlikely to produce any clinically significant adverse effects. Moreover, in women receiving concomitant androgen therapy, the addition of zinc may enhance therapeutic outcomes. Further research through well-designed and adequately powered clinical trials may be warranted to establish risk factors and parameters of benefit to shape clinical guidelines for integration of zinc and other nutrients into therapeutic strategies using exogenous estrogens.
Evidence: Famotidine (Pepcid RPD, Pepcid, Pepcid AC), ranitidine (Zantac).Similar properties but evidence lacking for extrapolation: Nizatidine (Axid, Axid AR); combination drug: ranitidine, bismuth, and citrate (Tritec).Similar properties but evidence indicating no or reduced interaction effects: Cimetidine (Tagamet, Tagamet HB).Extrapolated, based on similar properties:Antacids:Aluminum carbonate gel (Basajel), aluminum hydroxide (Alternagel, Amphojel); combination drugs: aluminum hydroxide, magnesium carbonate, alginic acid, and sodium bicarbonate (Gaviscon Extra Strength Tablets, Gaviscon Regular Strength Liquid, Gaviscon Extra Strength Liquid); aluminum hydroxide and magnesium hydroxide (Advanced Formula Di-Gel Tablets, Co-Magaldrox, Di-Gel, Gelusil, Maalox, Maalox Plus, Mylanta, Wingel); aluminum hydroxide, magnesium trisilicate, alginic acid, and sodium bicarbonate (Alenic Alka, Gaviscon Regular Strength Tablets); calcium carbonate (Titralac, Tums); magnesium hydroxide (Phillips’ Milk of Magnesia MOM); combination drugs: magnesium hydroxide and calcium carbonate (Calcium Rich Rolaids); magnesium hydroxide, aluminum hydroxide, calcium carbonate, and simethicone (Tempo Tablets); magnesium trisilicate and aluminum hydroxide (Adcomag trisil, Foamicon); magnesium trisilicate, alginic acid, and sodium bicarbonate (Alenic Alka, Gaviscon Regular Strength Tablets); combination drug: sodium bicarbonate, aspirin, and citric acid (Alka-Seltzer).Proton pump inhibitors:Esomeprazole (Nexium), lansoprazole (Prevacid, Zoton), omeprazole (Losec, Prilosec), pantoprazole (Protium, Protonix, Somac), rabeprazole (AcipHex, Pariet).See also Calcium and Calcium-Based Antacids in Nutrient-Nutrient Interactions. | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, Not Requiring Professional Management |
Probability:
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XXXEffect and Mechanism of Action
The solubility of the diverse zinc salts is affected by pH, which may vary between pH 1 and 7 under various physiological conditions in the stomach. Zinc absorption is optimal at an intragastric pH of 3 or less. Thus, by reducing gastric acid secretion, H 2 blockers (as well as proton pump inhibitors, and possibly antacids) can exert both direct and indirect effects on the absorption of zinc and result in depletion over time.
Through its important role in the healthy function of mucous membranes and recovery from injury, zinc supports the repair of damaged gastric tissue.
Research
The basic physiological premises of gastric pH environment effects on zinc absorption are generally agreed on, but research-based evidence into the clinical implications of this interaction, although consistent, is limited. Using a rodent model, Pinelli et al. found that cimetidine and nizatidine may reduce zinc absorption by decreasing gastric acid secretion and can deplete zinc levels in the prostate gland. In a series of experiments involving 16 healthy subjects, Sturniolo et al. compared the effects of inhibition of gastric acid secretion by ranitidine and cimetidine on zinc absorption. First, they performed a zinc tolerance test (ZTT, with ZnSO 4 , 220 mg orally), then administered cimetidine (1 g daily for 3 days), and observed decreased zinc absorption. Next, they administered oral doses of ranitidine (300 mg) daily for 6 days, 3 days before testing and 3 days during the test; they also administered 500 mg cimetidine to these subjects. Overall, they observed that the “areas under the plasma concentration curves for zinc were significantly reduced after ranitidine…, but not after cimetidine administration. Gastric acid was also reduced after ranitidine, but not after cimetidine (500 mg) administration, suggesting that gastric acid secretion plays a role in the regulation of zinc absorption in man.” In a two-way, four-phase, crossover study involving 10 healthy subjects (five males and five females), Henderson et al. investigated the effect of intragastric pH on zinc absorption. After a 9-hour fast, they administered a single oral dose of 50 mg elemental zinc as the acetate or the oxide salt and under either high or low intragastric pH conditions while continuously monitoring intragastric pH using a Heidelberg capsule pH detector-transmitter. “During the high pH phases, single oral doses of famotidine 40 mg oral suspension were administered before the zinc to raise the intragastric pH above 5. Intragastric pH < or = 3 was maintained in the low pH phases.” They found that the “highest zinc plasma concentrations occurred with the acetate salt at a low intragastric pH, while the lowest plasma concentrations occurred with the oxide salt at a high intragastric pH.” Subsequently, in vitro tests verified the importance of pH to the dissolution of these salts.
Notably, numerous clinicians and researchers have reported benefits for gastric tissue damaged by ulceration. In a double-blind trial involving 18 patients with benign gastric ulcers and no evidence of zinc deficiency, Frommer found that subjects administered zinc sulfate (220 mg orally three times daily) “had an ulcer healing rate three times that of patients treated with placebo,” and that “complete healing of ulcers occurred more frequently in the patients taking zinc.” These findings suggest that zinc may have independent therapeutic value in the treatment of individuals with gastric ulcer disease and related conditions, and that coadministration might provide synergistic effects.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians prescribing H 2 blockers (as well as proton pump inhibitors or antacids) are advised to coadminister elemental zinc, 50 to 75 mg daily (preferably as the acetate), to prevent the probable adverse effect of zinc depletion with chronic suppression of gastric acid.
Bumetanide (Bumex), ethacrynic acid (Edecrin), furosemide (Lasix), torsemide (Demadex). | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, with Professional Management |
Probability:
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The use of loop diuretics may result in increased urinary excretion of zinc.
Research
In a small, randomized trial, Wester compared urinary zinc excretion in nine patients during treatment with bendroflumethiazide, chlorthalidone, and hydrochlorothiazide with that in nine patients treated with bumetanide, furosemide, and triamterene. He observed that in patients receiving loop diuretics, “urine zinc concentration diminished and the total amount of zinc excretion increased much less than during therapy with the thiazides.” Based on these preliminary findings, the author concluded that “the observed increased urinary losses of zinc deserve further attention.”
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians prescribing a loop diuretic are advised to consider preliminary data suggesting that these medications may deplete zinc through increased urinary excretion. The risk of clinically significant zinc deficiency has not been established, but the probability of adverse effects is greater in individuals with compromised nutrient intake and concomitant medications that adversely affect zinc status. Dietary intake of zinc is often inadequate and zinc status impaired in many populations likely to be prescribed diuretics, such as patients with heart failure. Pending further research, medically supervised coadministration of zinc at a moderate dosage level, 40 to 80 mg elemental zinc once daily, is advisable as generally safe, unlikely to produce any clinically significant adverse effects, and potentially beneficial. Monitoring serum copper periodically and coadministering low-dose copper (e.g., 1-3 mg/day) are judicious means of guarding against zinc-induced copper deficiency with long-term zinc administration.
Metronidazole, Vaginal (MetroGel-Vaginal) | Beneficial or Supportive Interaction, with Professional Management |
Probability:
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XXXEffect and Mechanism of Action
The reported antitrichomonal properties of zinc sulfate appear to combine with metronidazole to produce an additive or synergistic interaction exerting greater therapeutic effect. No specific mechanism of action has been established.
Research
In a retrospective case analysis, Houang et al. reported the successful treatment of four patients with chronic recurrent trichomoniasis, without evidence of reinfection, using a combination of “zinc sulfate douching (1%) followed by a metronidazole 500 mg suppository per vaginale twice daily and 200 to 400 mg three times a day orally. The douching and suppository were used prophylactically for 3 nights after menstruation for some months.” These clinicians found that the addition of zinc sulfate douche greatly increased therapeutic efficacy in four patients “who had a history of 4 months to 4 years of culture-positive symptomatic trichomoniasis and received a variety of therapies before referral” and for whom vaginal metronidazole treatment alone had been ineffective. All four subjects remained asymptomatic and exhibited normal results in clinical and laboratory examinations at 2 to 5 months after treatment.
Further research with well-designed and adequately powered clinical trials may be warranted to confirm the efficacy of a combination zinc sulfate douche and metronidazole regimen in the treatment of vaginal trichomoniasis, as well as vaginal infection involving other organisms.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians treating women with vaginal trichomoniasis, especially recurrent or recalcitrant, are advised to consider concomitant prescription of zinc sulfate douche (1%) with metronidazole gel suppository. Adverse effects from zinc or from the combined intervention are unlikely to be greater than those associated with metronidazole alone, and the synergistic effect from coadministration may hasten or potentiate the treatment.
COX-1 inhibitors:Diclofenac (Cataflam, Voltaren), combination drug: diclofenac and misoprostol (Arthrotec), diflunisal (Dolobid), etodolac (Lodine), fenoprofen (Dalfon), furbiprofen (Ansaid), ibuprofen (Advil, Excedrin IB, Motrin, Motrin IB, Nuprin, Pedia Care Fever Drops, Provel, Rufen); combination drug: hydrocodone and ibuprofen (Reprexain, Vicoprofen); indomethacin (indometacin; Indocin, Indocin-SR), ketoprofen (Orudis, Oruvail), ketorolac (Acular ophthalmic, Toradol), meclofenamate (Meclomen), mefenamic acid (Ponstel), meloxicam (Mobic), nabumetone (Relafen), naproxen (Aleve, Anaprox, Naprosyn), oxaprozin (Daypro), piroxicam (Feldene), salsalate (salicylic acid; Amigesic, Disalcid, Marthritic, Mono Gesic, Salflex, Salsitab), sulindac (Clinoril), tolmetin (Tolectin).COX-2 inhibitor:Celecoxib (Celebrex). | Impaired Drug Absorption and Bioavailability, Precautions Appropriate | | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, with Professional Management | | Bimodal or Variable Interaction, with Professional Management | | Potential or Theoretical Beneficial or Supportive Interaction, with Professional Management |
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Low zinc levels may be associated with inflammatory conditions such as rheumatoid arthritis (RA). Anti-inflammatory agents such as NSAIDs may increase zinc excretion and contribute to zinc depletion.
Although not fully elucidated, zinc and other metals may complex with some NSAIDs to decrease absorption and bioavailability of both agents. Other mechanisms are also probable but unknown.
Research
Data from human studies indicate that NSAIDs can increase urinary zinc excretion but differ as to whether serum zinc levels, a marginally accurate marker, may reflect these alterations. Elling et al. conducted a study using healthy volunteers to assess the effect of naproxen, as a representative NSAID, on zinc metabolism. They observed a “significant increase in the urinary zinc excretion rate” in subjects administered naproxen, “with a mean increase in the order of 35%,” which fell toward normal at the end of treatment and returned to normal after withdrawal of naproxen. Notably, the “serum zinc concentration was virtually unchanged” during the treatment period. Although noting that the mechanism by which naproxen induces hyperzincuria was “not known” at the time, the authors suggested that increased zinc excretion could result from “protein binding interaction or a direct renal action of naproxen implying a decrease in the maximum tubular reabsorption capacity (Tmax).” They concluded that trials of longer duration, particularly involving patients with RA, “are needed, however, in order to evaluate the possibility of a zinc depletion.” That same year (1980), Balogh et al. investigated total plasma zinc levels in patients with RA being treated with a variety of medications. They found “significantly lower zinc levels in patients with rheumatoid arthritis on nonsteroidal anti-inflammatory drugs than in patients on levamisole and penicillamine.” Moreover, zinc levels “correlated positively with serum albumin, and there was an inverse correlation between zinc levels and both ESR and globulin concentration in all rheumatoid patients.” The authors concluded that their findings “support the hypothesis that low plasma zinc level in rheumatoid arthritis is one of the nonspecific features of inflammation.”
Dendrinou-Samara et al. conducted in vitro experiments that demonstrated the formation of complexes between anti-inflammatory medications and Zn(II), as well as other metal ions. In particular, they synthesized and characterized complexes of “Zn(II), Cd(II) and Pt(II) metal ions with the anti-inflammatory drugs, 1-methyl-5-(p-toluoyl)-1H-pyrrole-2-acetic acid (Tolmetin), alpha-methyl-4-(2-methylpropyl) benzeneacetic acid (Ibuprofen), 6-methoxy-alpha-methylnaphthalene-2-acetic acid (Naproxen) and 1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid (indomethacin).” They noted that “antibacterial and growth inhibitory activity is higher than that of the parent ligands.”
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Health care professionals are advised to consider coadministration of zinc when providing care to individuals using NSAIDs or other anti-inflammatory agents on a chronic basis for the treatment of inflammatory conditions such as RA. Broad and specific data indicate that these patients are at increased risk of compromised zinc status because of their nutrient intake and pathophysiological changes, and that these agents may further deplete zinc. Such depletion patterns may not be easily detected through standard laboratory tests; for example, serum zinc may not predictably reveal zinc deficiency in tissue or cells. Specific evidence-based research is lacking to confirm efficacy, but the use of concomitant zinc at physiologic levels, 15 to 40 mg elemental zinc daily, is generally safe and unlikely to produce any clinically significant adverse effects. However, separation of intake by at least 2 hours is prudent given the limited but pharmacologically reasonable data suggesting the possibility of chelate formation with simultaneous intake.
Penicillamine ( D-penicillamine; Cuprimine, Depen).Extrapolated, based on similar properties: Tetrathiomolybdate (investigational). END_ | Beneficial or Supportive Interaction, with Professional Management | | Bimodal or Variable Interaction, with Professional Management | | Impaired Drug Absorption and Bioavailability, Precautions Appropriate | | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, with Professional Management | | Potential or Theoretical Adverse Interaction of Uncertain Severity |
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Wilson's disease is a rare but potentially fatal autosomal recessive inherited disease of copper accumulation in the liver in which a defect in a copper-transport adenosine triphosphatase results in a failure of biliary excretion of excess copper.
Zinc and penicillamine can both be used in the treatment of individuals with Wilson's disease because of their effects of lowering copper levels, although by different mechanisms. Zinc produces its unique anticopper action by inducing intestinal cell metallothionein, which then forms a mucosal block, preventing copper absorption and increasing copper excretion in the stool. “Because this mechanism blocks not only the absorption of food copper but the reabsorption of large amounts of endogenously secreted copper, zinc serves to remove copper from the body as well as prevent its reaccumulation.” On the other hand, penicillamine can effectively increase urinary excretion of copper and reverse positive copper balance through its action as a chelating drug, but is also known for adverse effects.
However, the simultaneous intake of zinc and penicillamine may result in impaired efficacy and nutrient depletion. When ingested close together, penicillamine and zinc, as a supplement or through zinc-rich or zinc-enriched foods, may bind, resulting in reduced bioavailability of both agents. Moreover, penicillamine, through its chelating effect, may cause an unintentional increase in urinary excretion of zinc, along with the intended copper excretion. Effects will vary with mode of administration; the maximal plasma penicillamine concentrations achieved with oral penicillamine are only one-fifth that achieved by injection.
Research
Different forms of zinc have been used in the treatment of Wilson's disease, with zinc acetate used directly and zinc sulfate combined with penicillamine. Anderson et al. reviewed trials and case reports concerning zinc acetate as maintenance therapy in patients initially treated with a chelating agent. They concluded: “Although studies evaluating large populations are lacking, zinc therapy has demonstrated exceptional safety and efficacy over a period of 40 years…. Zinc acetate is an effective maintenance therapy for patients with Wilson's disease.” They further noted that with its “negligible toxicity, compared with that of previously approved treatments, zinc acetate is considerably safer than other treatments and can be used during pregnancy and for the treatment of presymptomatic patients.” They cautioned, however, that “data do not support its use as monotherapy in patients with acute neurologic or hepatic disease.”
Li et al. conducted a clinical trial, with long-term follow-up (4-11 years) of 31 children, investigating combined therapy with “large-dose zinc sulfate and low-dose penicillamine” in children with Wilson's disease (hepatolenticular degeneration, HLD). During the active phase of treatment, they treated symptomatic pediatric patients with “large-dose zinc sulfate (100-150 mg, <6 yr; 150-200 mg, 6-8 yr; 200-300 mg, 9-10 yr; 300 mg, >10 yr; 3 times a day) in addition to low-dose penicillamine (8-10 mg/kg/d).” Presymptomatic patients received zinc sulfate alone, as did patients receiving maintenance therapy when clinical improvement was achieved. They reported that “blood concentrations of copper were persistently lower than normal” and that “urine copper excretion of 24 hours was significantly lower than that before the combined therapy in all patients,” and it became normal in five cases (16%) after 6 months of treatment, and in 26 cases (84%) after 1 to 2 years of treatment. They also observed “higher blood concentrations of zinc” in 20 subjects (65%), with “higher urine zinc excretion … in 25 cases (81%) once or more times during the therapy.” They concluded that combined treatment with “large-dose zinc sulfate and low-dose penicillamine is an effective, safe and cheap treatment for children with HLD.”
Thus, the limited data from clinical trials indicate that zinc and penicillamine can be safely and effectively used together as part of a long-term strategy in the treatment of copper accumulation diseases, particularly Wilson's disease, but that timing and dosage need to be adjusted at different phases of the treatment based on patient response.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians treating individuals with Wilson's disease may enhance clinical outcomes and reduce adverse effects through implementation of an integrative therapeutic strategy combining zinc and chelating agents such as penicillamine or tetrathiomolybdate (investigational). Oral zinc sulfate and zinc acetate have both been used successfully in clinical trials. However, many clinicians consider zinc sulfate an inferior form with limited bioavailability. Zinc acetate, on the other hand, has superior bioavailability but may require a prescription, mainly because of its use in treating Wilson's disease. In all cases, the timing of zinc administration will depend on patient condition and response, with some researchers and clinicians relying primarily on chelating agents during the more severe stages of treatment and using zinc primarily for maintenance once a patient has stabilized or in presymptomatic patients. Zinc and copper chelators are best used sequentially rather than simultaneously because copper chelators also chelate zinc, although they are sometimes used concurrently. In all cases, separation of intake by at least 2 hours is recommended to minimize the risk of the two agents complexing and becoming less bioavailable. Close clinical management by trained and experienced health care professionals, with supervision and regular monitoring, is essential. Further study is warranted and probable given the body of evidence and practice supporting coadministration and sequential administration.
Evidence: Amiloride (Midamor), triamterene (Dyrenium).Similar properties but evidence indicating no or reduced interaction effects: Amiloride combination drug: amiloride and hydrochlorothiazide (Moduretic).Similar properties but evidence lacking for extrapolation: Spironolactone (Aldactone), spironolactone and hydrochlorothiazide (Aldactazide), triamterene and hydrochlorothiazide (Dyazide, Maxzide). | Bimodal or Variable Interaction, with Professional Management | | Drug-Induced Effect on Nutrient Function, Supplementation Contraindicated, Professional Management Appropriate | | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, with Professional Management |
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Potassium-sparing diuretics demonstrate varied effects on zinc metabolism. Amiloride may induce zinc accumulation (and potential toxicity) by significantly reducing zinc excretion; however, this effect appears to be dose related and may not compensate for zinc loss caused by concomitant diuretics such as hydrochlorothiazide. Conversely, triamterene appears to increase urinary zinc excretion in the short term and may cause depletion over time. Overall, the mechanisms by which thiazide diuretics affect zinc metabolism are incompletely known, although their blocking of reabsorption in the distal tubule is a plausible extrapolation from the known mechanism involving magnesium.
Research
Wester conducted several studies of experiments investigating the effects of various diuretics on urinary zinc excretion and tissue levels of zinc. In one paper he reported that 2 weeks of treatment with triamterene increased urinary zinc excretion by 18% compared with baseline.
The situation with amiloride is both more complicated and less clear in its implications. In a review, Reyes et al. suggest that a 10-mg dose of amiloride can significantly reduce urinary zinc excretion, but not 5 mg. Such an effect introduces the potential for excess zinc accumulation, although the effect is dose related, and the patient population is characterized by a relatively high incidence of inadequate zinc nutriture. Moreover, decreased zinc excretion does not inherently result in elevated zinc levels, given the homeostatic regulation of zinc absorption and the dynamic metabolic processes of zinc pools.
Two trials have investigated the effects of an amiloride-thiazide combination on zinc metabolism and nutriture, with mixed conclusions. Golik et al. compared serum zinc levels and urinary zinc excretion in 15 patients with essential hypertension taking a combination of hydrochlorothiazide and amiloride as chronic monotherapy, eight patients maintained with hydrochlorothiazide alone, and eight control subjects. Although “serum zinc values were statistically comparable in all three groups,” they found that “urinary zinc excretion was abnormally elevated in the two patient groups.” These authors concluded that, at least “in the dosage used, amiloride did not have a zinc-sparing effect.” That same year (1987), Verho et al. published a paper reporting their findings in a double-blind, parallel-group study comparing the effects of hydrochlorothiazide (50 mg) plus amiloride (5 mg) once daily versus piretanide (6 mg) once or twice daily on serum levels of zinc and other trace elements over 3 months in subjects with mild to moderate hypertension. They concluded that 3 months’ therapy with “a thiazide-potassium sparer diuretic combination is safe without producing any disturbances in the serum levels of trace elements,” based on the findings that urinary zinc excretion stayed within normal levels. The use of serum zinc to evaluate effects on zinc status in both studies limits the utility of conclusions based on their findings, but suggests that the depleting effects of the thiazide agent and the zinc-conserving effects of the potassium-sparing diuretic may neutralize each other in some cases. Nevertheless, the effects of these agents on tissue zinc stores and zinc pools deserve further research to determine the long-term effects of these drugs in a patient population with a relatively high incidence of subclinical zinc deficiency.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians prescribing potassium-sparing diuretics are advised to monitor zinc status closely in all patients. However, early symptoms of zinc deficiency, such as hypogeusia (decreased taste sensation), hyposmia (decreased olfactory sensation), diminished male sexual function, increased incidence of infections, slower wound healing, and white spots in fingernails, may be more useful than relying on monitoring of zinc levels in serum or elsewhere, because consensus is lacking as to an adequate laboratory standard for accurate assessment. Patients should be instructed to report any such occurrences. Triamterene can readily cause zinc depletion in the short term and with chronic use and, despite some suggestions to the contrary, the risk of zinc depletion with amiloride cannot be excluded, particularly in individuals with potential risk of marginal zinc status and increased susceptibility to zinc toxicity. Thus, coadministration of zinc at physiologic levels, 15 to 40 mg elemental zinc daily, may be indicated in patients receiving long-term triamterene and possibly other potassium-sparing diuretics.
The risk of zinc accumulation with amiloride use remains controversial, but close supervision and regular monitoring are always judicious in patients at greater risk for zinc toxicity, such as occurs with pregnancy, alcoholism, or renal insufficiency. Inherently, the probability of such risk being clinically significant would be greater in patients taking amiloride at a higher dose. Combining a thiazide diuretic with amiloride to mitigate its possible adverse effects may not provide a safe and simple remedy because these drugs deplete not only zinc but also other nutrients. Moreover, the mechanisms through which thiazide diuretics affect the metabolism of zinc and other minerals have not been fully elucidated, and the physiological effects of this proposed “pharmacological balancing act” have not been confirmed by substantive evidence from high-quality clinical trials.
Radiotherapy, external radiation therapy. | Prevention or Reduction of Drug Adverse Effect |
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Loss or alteration of taste sensation is a common adverse effect of radiation therapy in oncology patients, particularly in those receiving external radiotherapy (ERT) to the head and neck region. Zinc is known to play a central role in taste sensation, as well as the synergistic function of olfaction. Coadministration of zinc during and after radiotherapy may mitigate adverse effects on taste sensation and support recovery from such damage.
Research
Limited research indicates that administration of zinc during or after radiotherapy may reduce adverse effects of radiation on taste perception, but that benefit is less likely in patients experiencing loss of taste perception resulting from hemodialysis. Ripamonti et al. investigated the administration of oral zinc sulfate in preventing and correcting taste abnormalities for four taste qualities in cancer patients before, during, and after receiving radiotherapy to the head and neck region. They randomized 18 patients to receive either zinc sulfate tablets (45 mg per dose) or placebo three times daily “at the onset of subjective perception of taste alterations during the course of ERT and up to 1 month after ERT termination.” After noting that “taste acuity for one or more taste qualities was already impaired before ERT,” they reported that “taste alterations were experienced at least once for a minimum of 3 of the 8 measured thresholds by 100% of the patients” during ERT treatment, and that “33.3% of the patients became aware of some alteration within the first week of treatment.” When treatment (or placebo) was initiated after appearance of such adverse effects, they found that “patients treated with placebo experienced a greater worsening of taste acuity during ERT treatment compared with those treated with zinc sulfate,” and that “one month after ERT was terminated, the patients receiving zinc sulfate had a quicker recovery of taste acuity than those receiving placebo.” In particular, “statistically significant differences between the two groups emerged for urea detection and sodium chloride recognition thresholds during ERT treatment and for sodium chloride, saccharose, and hydrogen chloride recognition thresholds after the termination of ERT treatment.” These researchers concluded that “pharmacologic therapy [with zinc] is effective and well tolerated; it could become a routine in clinical practice to improve the supportive care of patients with taste alterations resulting from head and neck cancer.”
In relevant but unrelated research, Matson et al. conducted a double-blind, randomized, placebo-controlled study involving 15 stable hemodialysis patients. They found that zinc sulfate, 220 mg daily for 6 weeks, “does not improve the disturbance of taste perception,” particularly for the sour modality, in hemodialysis patients.
These two preliminary studies indicate that further research is warranted through well-designed clinical trials investigating the mechanisms of action in preventing and recovering taste sensation, how that differs in relation to iatrogenic cause, and whether prophylactic zinc coadministration might produce better outcomes than reactive prescribing.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians administering radiotherapy, particularly to patients with head and neck cancers, may prevent or reverse alteration or loss of taste sense, which often occurs as a result of such therapy, through concomitantly prescribing 40 to 60 mg elemental zinc daily. Use of zinc at this dosage level is unlikely to produce any adverse effects, if complemented with low-dose copper, or interfere with conventional oncological therapies.
Evidence: Demeclocycline (Declomycin), minocycline (Dynacin, Minocin, Vectrin), tetracycline (Achromycin, Actisite, Apo-Tetra, Economycin, Novo-Tetra, Nu-Tetra, Sumycin, Tetrachel, Tetracyn); combination drugs: chlortetracycline, demeclocycline and tetracycline (Deteclo); bismuth, metronidazole and tetracycline (Helidac).Extrapolated, based on similar properties: Oxytetracycline (Terramycin).Similar properties but evidence indicating no or reduced interaction effects: Doxycycline (Atridox, Doryx, Doxy, Monodox, Periostat, Vibramycin, Vibra-Tabs).See also Antibiotics and Antimicrobial Agents (Systemic). | Impaired Drug Absorption and Bioavailability, Precautions Appropriate | | Bimodal or Variable Interaction, with Professional Management | | Drug-Induced Adverse Effect on Nutrient Function, Coadministration Therapeutic, with Professional Management |
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Tetracycline and some related antibiotics tend to form relatively insoluble chelates with zinc salts (and other divalent and trivalent metal ions) and thereby impair absorption and therapeutic activity of both agents. In contrast to other members of the tetracycline class, doxycycline and zinc do not appear to interact to a clinically significantly degree.
Research
The scientific literature on the effects of zinc on bioavailability of tetracycline antibiotics is generally considered as constituting a well-documented consensus, although specific research from human trials is limited. Penttila et al. conducted a crossover study involving seven volunteers to compare the effect of zinc sulfate on the absorption of tetracycline and doxycycline. They reported that when a single dose of zinc sulfate (45 mg elemental zinc) was given simultaneously with tetracycline hydrochloride (500 mg) or doxycycline chloride (200 mg), the “serum concentration of tetracycline, the area under the serum tetracycline concentration-time curve and the excretion of tetracycline in urine were reduced by about 30%… from the respective control values,” but the “absorption of doxycycline was not influenced significantly.” Overall, they concluded that the “clinical significance of the zinc-tetracycline interaction seems to be of limited importance.” Andersson et al. published similar findings regarding intestinal absorption of zinc in their study of eight healthy volunteers administered 50 mg elemental zinc orally. That same year (1976), Mapp and McCarthy found that “absorption of 250 mg phosphate-potentiated tetracycline hydrochloride was reduced by 75% when administered concurrently with 220 mg zinc sulphate.”
Minimal research has focused on the effects of tetracycline on zinc absorption and clinical implications of long-term use. In rodent studies, administration of tetracycline was reported to result in increased elimination rate of zinc, which could originate in zinc-tetracycline interactions in blood plasma. However, after “using clinical data relative to fasting subjects as taken from the literature” to perform computer simulations of zinc-tetracycline interactions in the GI fluid, Brion et al. concluded that “no significant effect can be expected from tetracyclines on the distribution of zinc in plasma at the usual therapeutic levels.” Nevertheless, the authors added that “zinc-tetracycline interactions have been found to be determining factors for the bioavailabilities of the metal as well as of the antibiotic in the gastrointestinal fluid.” No studies have been conducted to determine the effects of chronic or repeated tetracycline antibiotics on zinc status and function in humans.
Weimar et al. and Michaelsson et al. demonstrated that patients with dermatitis herpetiformis, acne, psoriasis, and Darier's disease have low epidermal zinc concentrations. Notably, “mean serum zinc concentration was, however, significantly decreased only in men with dermatitis herpetiformis.”
Clinical Implications and Adaptations
Physicians prescribing tetracycline antibiotics are advised to ask patients about their supplement use and to tell them to separate intake of zinc supplements, multimineral formulation, and zinc-rich food (as well as other mineral intake) by at least 2 hours before or 4 hours after the medication. Such precautions would also prevent the potential depletion of zinc by the tetracyclines by avoiding chelate formation. In patients being treated for acne, especially inflammatory acne, coadministration of 30 to 45 mg elemental zinc daily, as zinc acetate, citrate, gluconate, or other highly bioavailable forms, may be indicated and can be efficacious, assuming compliance with intake separation. Zinc sulfate has been less effective and associated with greater incidence of adverse effects. When both agents are indicated, consider prescribing doxycycline, a noninteracting tetracycline.
Bendroflumethiazide (bendrofluazide; Naturetin); combination drug: bendrofluazide and propranolol (Inderex); benzthiazide (Exna), chlorothiazide (Diuril), chlorthalidone (Hygroton), cyclopenthiazide (Navidrex); combination drug: cyclopenthiazide and oxprenolol hydrochloride (Trasidrex); hydrochlorothiazide (Aquazide, Esidrix, Ezide, Hydrocot, HydroDiuril, Microzide, Oretic), hydroflumethiazide (Diucardin), methyclothiazide (Enduron), metolazone (Zaroxolyn, Mykrox), polythiazide (Renese), quinethazone (Hydromox), trichlormethiazide (Naqua).Similar properties but evidence lacking for extrapolation: Spironolactone (Aldactone); combination drugs: hydrochlorothiazide and amiloride (Moduretic); hydrochlorothiazide and captopril (Acezide, Capto-Co, Captozide, Co-Zidocapt); hydrochlorothiazide and enalapril (Vaseretic); hydrochlorothiazide and lisinopril (Prinzide, Zestoretic); hydrochlorothiazide and losartan (Hyzaar); hydrochlorothiazide and metoprolol (Lopressor HCT); spironolactone and hydrochlorothiazide (Aldactazide); triamterene and hydrochlorothiazide (Dyazide, Maxzide).See also Amiloride in Potassium-Sparing Diuretics. | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, with Professional Management |
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Thiazide diuretics can increase urinary zinc excretion and result in zinc loss with either single-dose or long-term use. Long-term thiazide therapy may cause significant zinc depletion, particularly in individuals with preexisting impaired zinc status, compromised nutrient intake, or medical conditions susceptible to zinc deficiency. The mechanism of thiazide diuretics’ effect on zinc is poorly understood, but these agents act primarily on the initial portion of the distal convoluted tubule in the nephron; hormone-mediated processes may also be involved.
Research
In a small, randomized trial, Wester compared urinary zinc excretion in nine patients during treatment with bendroflumethiazide, chlorthalidone, and hydrochlorothiazide with that in nine patients treated with bumetanide, furosemide, and triamterene. He observed that in patients receiving thiazide diuretics, “the zinc concentration rose by 30% and the total amount of zinc excretion increased by 60%.” Based on these preliminary findings, the author concluded that “the observed increased urinary losses of zinc deserve further attention.”
In a review, Reyes cautioned that the probability of a clinically significant zinc deficiency with thiazide diuretics is greater in pregnant women and individuals with hepatic cirrhosis, diabetes mellitus, GI disorders, renal insufficiency, and alcoholism, that is, conditions associated with diminished total body zinc levels. Likewise, in related research, Golik et al. determined that individuals with type 2 diabetes mellitus and congestive heart failure “excrete larger amounts of zinc, which may eventually lead to zinc deficiency.” These findings bear directly on the data relating to hypertensive medications, given the use of diuretics for heart failure and the high incidence of comorbid hypertension among these patient populations.
The combination of amiloride with a thiazide combination, as a means of mitigating the adverse effects of both agents on zinc metabolism and nutriture, is discussed in the Potassium-Sparing Diuretics section. Similarly, the concomitant use of hydrochlorothiazide and ACE inhibitors may further exacerbate zinc loss; this interaction is reviewed in Captopril, Enalapril, and related Angiotensin-Converting Enzyme (ACE) Inhibitors.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians prescribing thiazide diuretics are advised to coadminister zinc (50-100 mg elemental zinc daily) to compensate for possible drug-induced zinc loss and prevent zinc depletion. Monitoring for zinc deficiency is appropriate but is compromised by the limited sensitivity of laboratory assessment in accurately detecting depletion of zinc at the tissue level. Advise patients to watch for signs of zinc depletion, especially those at greater risk for compromised nutrient intake or other factors likely to impair zinc status.
Coadministration of folic acid, magnesium, potassium, and calcium may also be appropriate to prevent adverse effects from thiazide diuretic on the physiological levels and functions of these nutrients and to advance the broader therapeutic goals of enhancing cardiovascular health.
Evidence: Divalproex semisodium, divalproex sodium (Depakote), sodium valproate (Depacon), valproate semisodium, valproic acid (Depakene, Depakene Syrup).Similar properties but evidence lacking for extrapolation: Carbamazepine (Carbatrol, Tegretol), clonazepam (Klonopin), clorazepate (Tranxene), ethosuximide (Zarontin), ethotoin (Peganone), felbamate (Felbatol), fosphenytoin (Cerebyx, Mesantoin), levetiracetam (Keppra), mephenytoin, mephobarbital (Mebaral), methsuximide (Celontin), oxcarbazepine (GP 47680, oxycarbamazepine; Trileptal), phenobarbital (phenobarbitone; Luminal, Solfoton), phenytoin (diphenylhydantoin; Dilantin, Phenytek), piracetam (Nootropyl), primidone (Mysoline), topiramate (Topamax), trimethadione (Tridione), vigabatrin (Sabril), zonisamide (Zonegran). | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, with Professional Management |
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Valproic acid (VPA) can alter zinc and copper homeostasis and may cause depletion of either or both minerals, not necessarily reflected in serum levels. The anticonvulsive activity of VPA on the brain may be “mediated through its effect on the metabolism of Zn in the brain and the concomitant changes in the activity of the zinc-dependent enzymes glutamic acid decarboxylase and carbonic anhydrase.”
Research
Animal and human studies of VPA's effect on zinc status have produced mixed findings. Using a rodent model, Hurd et al. found that VPA administration for 1 week produced significant depletion of plasma levels of zinc, as well as selenium. In a study of 15 children with primary epilepsy receiving long-term VPA treatment, Lerman-Sagie et al. found that serum and urine levels of zinc and copper levels were within normal limits, but erythrocyte zinc content was significantly lower than controls matched for age and gender. The authors interpreted their findings as suggesting that the antiseizure effect of valproate may be related to and/or mediated by its effect on zinc-dependent CNS enzymes. Subsequently, Kaji et al. investigated measured serum zinc and copper levels in epileptic children treated with VPA and/or other antiepileptic drugs (AEDs). They found that in “contrast to the reported results of animal experiments, serum Zn levels were not altered in patients with VPA treatment.” Notably, patients “treated with VPA monotherapy had significantly lower levels of serum Cu” than normal controls, as did those “treated with VPA in addition to some other AED.” Those “treated with AEDs except for VPA” exhibited serum copper concentrations “not statistically different from those of control subjects.” However, in a later trial involving 51 children with epilepsy, Sozuer et al. observed that patients treated with VPA, as monotherapy or in combination with carbamazepine, exhibited significantly lower levels of serum zinc than in the two control groups, consisting of seven untreated epileptic and 12 normal children. Because serum zinc and copper “concentrations of the untreated epileptics were not significantly different from those of normal controls,” the authors concluded that “serum trace metal homeostasis may be affected by AED therapy, but not by the convulsive disorder itself.”
Reports
In a letter, Simpson and Bryce-Smith reported cutaneous manifestations of zinc deficiency during treatment with anticonvulsants.
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians prescribing VPA, as monotherapy or in combination with other AEDs, will want to be watchful for deficiencies of zinc and numerous other key nutrients, especially in children and women of childbearing age. Given the lack of reliable measures of zinc deficiency, it is particularly important to instruct patients to be alert to signs of zinc deficiency, such as alterations in taste or smell sensation and increased frequency of infections. Although specific evidence-based research is lacking to confirm drug-induced depletion or efficacy of coadministration, the use of concomitant zinc at a low dosage level, 30 to 50 mg elemental zinc daily, would be prudent and is generally safe and unlikely to produce any clinically significant adverse effects. In children a dose of 10 mg elemental zinc twice daily is typical but can vary depending on the child's age and weight. Complementary daily copper, 1/115; to 1/120; the dose of zinc, would prevent copper deficiency resulting from the medication or the zinc intake.
Anisindione (Miradon), dicumarol, ethyl biscoumacetate (Tromexan), nicoumalone (acenocoumarol; Acitrom, Sintrom), phenindione (Dindevan), phenprocoumon (Jarsin, Marcumar), warfarin (Coumadin, Marevan, Warfilone). | Impaired Drug Absorption and Bioavailability, Precautions Appropriate | | Minimal to Mild Adverse Interaction—Vigilance Necessary | | Adverse Drug Effect on Nutritional Therapeutics, Strategic Concern |
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Zinc, as well as other minerals such as iron and zinc, may bind with warfarin or dicumarol and reduce bioavailability of the medication. Formation of such complexes might also reduce zinc absorption and bioavailability and could potentially interfere with the effectiveness of oral zinc as a preventive or therapeutic agent.
Research and Reports
Despite recurrent descriptions of this interaction as “well documented,” a search of the scientific literature provides no clinical trials or substantive case reports directly investigating or confirming evidence from in vitro experiments or extrapolations from interactions involving iron, calcium, or other minerals. Although reasonably predictable from a pharmacokinetics perspective, research into this area would be valuable given the large number of patients using nutritional supplements that contain zinc or other metals.
Clinical Implications and Adaptations
The chemistry of common mineral nutrients binding warfarin is well founded, but the frequency of occurrence is uncertain, its nature remains unclear, and conclusive evidence of the clinical significance of this interaction is lacking. Nevertheless, physicians prescribing warfarin are advised to recommend to patients that they separate warfarin administration from intake of zinc (or iron or magnesium) supplements by at least 2 hours. Regardless, physician-patient communication is especially important in the event that individuals undergoing anticoagulant therapy are taking zinc or any other mineral supplements. Nutritional support, including zinc, may be indicated in many patients likely to be on warfarin therapy given the high incidence of inadequate zinc nutriture among elderly and institutionalized individuals. Regular monitoring of international normalized ratio (INR) is critical so that warfarin levels can be adjusted accordingly when concomitant intake is deemed appropriate.
Evidence: Zidovudine (azidothymidine, AZT, ZDV, zidothymidine; Retrovir).Extrapolated, based on similar properties: Azidothymidine combination drugs: abacavir, lamivudine, and zidovudine (Trizivir); zidovudine and lamivudine (Combivir); didanosine (ddI, dideoxyinosine; Videx), dideoxycytidine (ddC, zalcitabine; Hivid), lamivudine (3TC, Epivir), stavudine (D4T, Zerit), tenofovir (Viread). | Drug-Induced Nutrient Depletion, Supplementation Therapeutic, with Professional Management | | Beneficial or Supportive Interaction, with Professional Management | | Bimodal or Variable Interaction, with Professional Management | | Potential or Theoretical Adverse Interaction of Uncertain Severity |
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Zinc plays a central role in many immune functions, including T-cell division, maturation, differentiation, and function; lymphocyte response to mitogens; programmed cell death of lymphoid and myeloid origins; gene transcription; and biomembrane function. Thymulin, a zinc-bound hormone, and Cu/Zn superoxide dismutase, as well as congenital or acquired zinc deficiencies, are associated with immune abnormalities and increased susceptibility to infectious diseases. AZT may deplete zinc (and other nutrients). Populations likely to have a high incidence of HIV infection may also be more likely to exhibit compromised zinc status, possibly due to malnutrition, progression of the pathology, or excessive ejaculation. “AIDS subjects suffer from reduced zinc bioavailability, more severe in stage IV than in stage III.”
Zidovudine may deplete plasma zinc levels; conversely, adequate zinc levels may enhance therapeutic response to AZT treatment. Zinc deficiency may diminish drug effectiveness because zidovudine requires thymidine kinase, a zinc-dependent enzyme, for conversion to its active triphosphate form. Notably, individuals with HIV infection, particularly later stages of AIDS, tend to exhibit elevated cooper levels.
Research
In a 1991 longitudinal study involving 37 HIV-positive participants, 15 treated with ZDV (AZT, 500-1200 mg/day) and 22 serving as untreated, CD4 level–matched controls, Baum et al. found significantly decreased mean plasma levels of zinc (and copper) in a “large proportion” of AZT-treated subjects after 12 months of antiviral therapy. Hematological and plasma nutrient levels were similar in both groups before treatment, but after therapy, “drug-treated subjects demonstrated alterations in hematological and nutritional parameters.” The authors noted that the “level of plasma zinc appeared to be particularly important in maintaining immune function in the ZDV-treated group. Whereas ZDV-treated subjects with adequate zinc levels displayed a significant increase in the response of peripheral blood lymphocytes to mitogens, this enhancement was not demonstrated in zinc-deficient, ZDV-treated participants or in untreated individuals whose lymphocyte response significantly declined over time, despite adequate zinc status.” The authors concluded that their findings “reveal a zidovudine-induced effect on nutritional parameters, indicating the importance of monitoring nutritional status with drug therapeutic regimens.” Subsequent papers by Baum et al. and Bogden et al. have emphasized the key physiological roles of zinc and the importance of zinc status in HIV infection, providing evidence that compromised nutritional and antioxidant status begins early in HIV-1 infection and may contribute to disease progression.
Although some survey data indicate that higher zinc intake may be associated with worse outcomes in HIV-positive individuals (regardless of AZT therapy), other trials suggest a potential synergistic benefit from coadministration in patients treated with AZT. In a survey of 281 HIV-positive homosexual/bisexual men, Tang et al. reported that increased intake (from food and supplements) of “zinc was monotonically and significantly associated with an increased risk of progression to AIDS.” In a follow-up paper the authors reported that “any intake of zinc supplements, however, was associated with poorer survival” and suggested that further “studies are needed to determine the optimal level of zinc intake in HIV-1-infected individuals.” Conversely, in a study investigating the relationship between zinc deficiency and survival in HIV-positive homosexual men, Campa et al. found that higher zinc levels were associated with better immune function and higher CD4+ cell counts, while zinc deficiency was associated with greater incidence of HIV-related mortality. Subsequently, Mocchegiani et al. conducted a clinical trial involving 17 AZT-treated stage III subjects with generalized lymphadenopathy and 12 stage IV/subgroup C1 AIDS patients, with 18 stage III subjects with generalized lymphadenopathy and 10 stage IV/subgroup C1 subjects treated only with AZT serving as controls. Stage III and stage IV/C1 patients administered zinc sulfate (200 mg daily for 30 days) exhibited an “increase or a stabilization in the body weight and an increase of the number of CD4+ cells and the plasma level of active zinc-bound thymulin,” and the “frequency of opportunistic infectious episodes in the 24 months following entry into the study was reduced after zinc supplementation in stage IV C1 subjects (11 infections versus 25 in controls) and delayed in stage III zinc-treated subjects (1 infection/24 months versus 13 infections/24 months in controls).” Notably, the beneficial effect of zinc on opportunistic infections was “restricted to infections due to Pneumocystis cariniiand Candida,whereas no variations have been observed in the frequencies of cytomegalovirusand toxoplasmainfections.” The authors concluded that these data “may support the benefit of zinc as an adjunct to AZT therapy in AIDS pathology.”
In a randomized, double-blind, placebo-controlled trial involving 96 children with HIV-1 infection in South Africa, Bobat et al. found that administering 10 mg daily of elemental zinc, as sulfate, reduced watery diarrhea significantly and lowered the incidence of pneumonia (compared to placebo), without adversely affecting (i.e., increasing) plasma HIV-1 viral load. In a randomized controlled trial involving 159 HIV-infected adults in Peru, with at least a 7-day history of diarrhea, Carcamo et al. found that 2 weeks of treatment with 50 mg zinc twice daily does not reduce or eliminate persistent diarrhea in adults infected with HIV. The authors added: “Longer treatment or follow-up beyond 2 weeks might have revealed treatment benefit…. Among children, however, benefits of zinc supplementation on diarrhea have been evident after the fourth day of supplementation.”
Nutritional Therapeutics, Clinical Concerns, and Adaptations
Physicians treating HIV-infected individuals with AZT or related antiretroviral regimens should always assess nutritional status, particularly dietary intake and use of antioxidant and other supplements, and consider coadministration of zinc, selenium, glutathione/ N-acetylcysteine, and other nutrients that may be beneficial. Multiple factors, including the underlying pathology, concomitant health and lifestyle factors, comorbid conditions, and the multiple medications often used, strongly suggest high susceptibility to compromised nutritional status, which may be further exacerbated by drug-induced nutrient depletion patterns.
Moderate-dose to high-dose zinc, 50 to 100 mg elemental zinc daily, may counter preexisting deficiency, reduce effects of drug-induced depletion, and facilitate the activity of AZT. Coadministration of 1 to 2 mg of copper may be appropriate (but may be contraindicated if serum/plasma levels are already high) to neutralize the potential risk of adverse effects on the immune system from the long-term zinc. Laboratory assessment of zinc status may be less than ideal, but regular monitoring of the nutritional and metabolic status of such patients is essential, including instructing the patient to be attentive to signs of possible zinc deficiency. Clinical management of HIV-positive patients using multiple treatment modalities in an individualized and evolving integrative strategy requires close collaboration and regular coordination among health care professionals trained and experienced in conventional pharmacology and nutritional therapeutics.
Acetylsalicylic acid (acetosal, acetyl salicylic acid, ASA, salicylsalicylic acid; Arthritis Foundation Pain Reliever, Ascriptin, Aspergum, Asprimox, Bayer Aspirin, Bayer Buffered Aspirin, Bayer Low Adult Strength, Bufferin, Buffex, Cama Arthritis Pain Reliever, Easprin, Ecotrin, Ecotrin Low Adult Strength, Empirin, Extra Strength Adprin-B, Extra Strength Bayer Enteric 500 Aspirin, Extra Strength Bayer Plus, Halfprin 81, Heartline, Regular Strength Bayer Enteric 500 Aspirin, St. Joseph Adult Chewable Aspirin, ZORprin); combination drugs: ASA and caffeine (Anacin); ASA, caffeine, and propoxyphene (Darvon Compound); ASA and carisoprodol (Soma Compound); ASA, codeine, and carisoprodol (Soma Compound with Codeine); ASA and codeine (Empirin with Codeine); ASA, codeine, butalbital, and caffeine (Fiorinal); ASA and extended-release dipyridamole (Aggrenox, Asasantin).
Salsalate (Salicylic acid; Amigesic, Disalcid, Marthritic, Mono Gesic, Salflex, Salsitab).
Indomethacin (Indometacin; Indocin, Indocin-SR).
See also Nonsteroidal Anti-inflammatory Drugs (NSAIDs); similar mechanisms involved.
In a 1982 letter, Ambanelli et al. reported that intake of 3 g aspirin daily can induce changes in serum and urinary zinc, observable beginning 3 days after initiation of aspirin; indomethacin was also implicated. Such an effect would generally be considered reasonably predictable based on scientific knowledge of the respective properties and activities of these agents. Further research would be warranted to determine the risks, clinical implications, and responsible countermeasures in individuals using aspirin chronically.
Conversely, in vitro experiments conducted by Kim et al. demonstrated attenuation of Zn 2+ neurotoxicity by aspirin attributed to the prevention of synaptically released Zn 2+ entry into neurons, primarily through voltage-gated Ca 2+ channels (VGCC), which can mediate pathological neuronal death. The authors noted that “aspirin derivatives lacking the carboxyl acid group did not reduce Zn 2+ neurotoxicity” and interpreted these findings as suggesting “that aspirin prevents Zn 2+ -mediated neuronal death by interfering with VGCC, and its action specifically requires the carboxyl acid group.” Further research may be warranted to determine potential clinical implications of these observations.
Evidence: Cholestyramine (Locholest, Prevalite, Questran).
Extrapolation: Colesevelam (WelChol), colestipol (Colestid).
Cholestyramine and other bile acid sequestrants are known to bind a multitude of nutrients, including zinc and other key minerals, in the gut, impairing bioavailability to the degree that depletion and deficiency may occur. However, research is limited and primarily derived from animal studies. Using a rodent model to investigate alterations in calcium, magnesium, iron, and zinc metabolism by cholestyramine, Watkins et al. found that, compared to controls, cholestyramine-fed rats exhibited “a lower net positive balance for magnesium, iron, and zinc” and “a decreased urinary zinc.” The authors hypothesized: “Alterations in calcium, magnesium, and zinc metabolism might be explained by inadequate vitamin D absorption from the intestine followed by an increased secretion of parathyroid hormone.” Regardless of the limited human research, concern for adverse effects on nutrient status in patients being treated with bile acid sequestrants is widespread among clinicians and researchers, and concomitant support with broad-spectrum multivitamin-mineral supplements is considered judicious, with the caveat that intake needs to be at least 2 hours before or 4 hours after the medication.
Alendronate (Fosamax), clodronate (Bonefos, Ostac), etidronate (Didronel), ibandronate (Bondronat, Boniva), pamidronate (Aredia), risedronate (Actonel), tiludronate (Skelid), zoledronic acid (Zometa).
With simultaneous intake, numerous minerals, including zinc, may bind with bisphosphonates and impair the absorption of all agents involved.
Although reasonable and consistent with present pharmacokinetic knowledge concerning other minerals, evidence from clinical trials directly substantiating the chelation interaction between zinc and bisphosphonates is lacking.
Preliminary data indicate other probable interactions between bisphosphonates and zinc. Adami et al. found that IV bisphosphonate administration “induced an acute-phase response (APR) irrespective of the underlying disease, manifested by a fall in circulating lymphocyte number and serum zinc concentration and in a rise in C-reactive protein.” Notably, in postmenopausal women with osteoporosis, alendronate significantly reduces the concentrations of urinary zinc. Thus, comparison of zinc excretion and biochemical markers of bone remodeling have been proposed in the assessment of the effects of alendronate and calcitonin on bone in postmenopausal women with osteoporosis.
Health care professionals treating individuals on bisphosphonate therapy for osteoporosis should inform patients of this probable chelation interaction and instruct them to separate oral intake, ingesting the zinc (and other minerals) 1 hour before or 2 hours after the bisphosphonate.
Zinc chelation may play a role in novel cancer therapies involving use of bisphosphonates to chelate zinc and thereby inhibit matrix metalloproteinases (MMPs), a family of zinc-dependent proteinases involved in the degradation of the extracellular matrix, a process on which cancer metastasis is believed to depend. In an in vitro experiment, Boissier et al. reported that bisphosphonates inhibited MMP proteolytic activity by breast and prostate carcinoma cells, and that this inhibitory effect of bisphosphonates on MMP activity was completely reversed in the presence of excess zinc. These areas of zinc-bisphosphonate interaction are currently being investigated.
Evidence: Clofibrate (Atromid-S).
Related: Bezafibrate (Bezalip), ciprofibrate (Modalim), fenofibrate (Tricor, Triglide, Lofibra), gemfibrozil (Apo-Gemfibrozil, Lopid, Novo-Gemfibrozil).
In addition to its antihyperlipidemic activity, clofibrate is known to alter serum protein patterns, including proteins associated with key minerals. Using a rodent model, Powanda et al. detected a “significant decrease in plasma zinc … after the rats were fed the 1.25% clofibrate diet for 1 week,” as well as “a significant decrease in hepatic zinc.” However, clofibrate did not affect the plasma concentration of α 2 -macroglobulin, although it did “selectively decrease the plasma concentration of two trace metal carrier proteins, transferrin and ceruloplasmin.” The authors noted that the observed reduction in the hepatic concentration of zinc “may merely be the result of a redistribution to achieve a new systemic equilibrium.” However, they also speculated that “the depression in plasma zinc reflects the marked decrease in transferrin, which is known to bind zinc, or is caused by the displacement of zinc from albumin by clofibrate.” Thus, despite offering several possible explanations for these findings, they declared that the “decrease in plasma zinc remains to be explained.”
Further research into the interaction between clofibrate and zinc is not readily discoverable through a standard search of the scientific literature. Follow-up research may be warranted given the increased knowledge of the manifold roles of zinc that has emerged since publication of this single paper.
Cyclosporine (Ciclosporin, cyclosporin A, CSA; Neoral, Sandimmune, SangCya).
Several secondary reference texts have declared, without citing specific and substantive evidence, that zinc should not be administered concomitantly with cyclosporine or other immunosuppressant drug regimens because of its “immunostimulant” activity. Emerging knowledge of the complex and nuanced function of zinc as a modulator of immune function in its interplay within the dynamic network and signaling model, such as suggested in the work of Candace Pert, Michael Ruff, and other pioneers of psychoneuroimmunology, as well as the continually shifting nature of its distribution, suggest that a simple characterization of zinc as “stimulating” the immune system is unlikely to offer a comprehensive explanation for the diverse effects observed in clinical practice and research settings. Consequently, a blanket contraindication of zinc coadministration appears speculative without substantive human research findings or qualified case reports documenting adverse effects, preferably with a clear elucidation of the mechanism(s) of action. Further research is warranted, with clinical supervision and monitoring being critical in the meantime, as always with patients undergoing any immunosuppressive therapy.
Metoclopramide (Reglan), olanzapine (Symbyax, Zyprexa).
In vitro studies with zinc suggest that it appears to modulate antagonist drug interactions with the D 1 dopamine receptor and the dopamine transporter. However, direct evidence, from clinical trials or substantive case reports, of a clinically significant adverse effect on the therapeutic activity of drugs that rely on dopamine receptor antagonists is lacking at this time. In an experimental setting, Schetz et al. demonstrated “the effect of zinc on the binding of D 1 - and D 2 -selective antagonists to cloned dopamine receptors and show that the inhibition by zinc is through a dose-dependent, reversible, allosteric, two-state modulation of dopamine receptors.” They found that zinc “exerts a low-affinity, dose-dependent, EDTA-reversible inhibition of the binding of subtype-specific antagonists primarily by decreasing the ligands’ affinity for their receptors,” and suggested that “the mechanism of zinc inhibition appears to be allosteric modulation of the dopamine receptor proteins.” Based on data from multiple investigators indicating that zinc “retards the functional effects of antagonist at the D 2 L receptor in intact cells,” research findings have been interpreted to “suggest that synaptic zinc may be a factor influencing the effectiveness of therapies that rely on dopamine receptor antagonists.” These in vitro studies suggest that zinc may interact with drugs that rely on dopamine receptor antagonists and indicate that further clinical research is warranted to determine the character and clinical significance of such an interaction.
Gillin et al. (1982) studied patients with acute and chronic schizophrenia, on or off treatment with various major tranquilizers, looking for significant deviations from normal in concentrations of zinc or copper in serum, urine, or gastric fluid, in serum ceruloplasmin or in hair zinc. Although depletion of body zinc and increases in brain copper have been associated with severe changes in mentation and personality, they found no differences. Research has already been reviewed to indicate that measurement of zinc deficiencies is unreliable and tentative, with multiple pools existing in the body and their concentrations not necessarily relating to levels found in plasma, urine, gastric fluid, or hair. Insufficient data exist even to guide zinc clinic trials because schizophrenia may be a heterogenous condition. Ten years later, Andrews (1992) suggested that male transmission of risk, the parental age effect, racial differences in birth seasonality, the disturbed gender ratios in the offspring of schizophrenic mothers, and the association between diabetes and schizophrenia are explained by changes to zinc homeostasis. The primary site of action of zinc deficiency was proposed to be the putative ZFY sex-determining system. Zinc deficiency was also linked to other mental disorders. During the 1970s, Pfeiffer and Bacchi reported successful outcomes in 95% of more than 400 patients diagnosed with pyrroluria-type schizophrenia using vitamin B 6 and zinc.
EDTA (Ethylenediaminetetraacetic acid).
In vitro experiments suggest that concomitant use with zinc might increase the cytotoxicity of cisplatin in the presence of EDTA, compared with cisplatin alone.
Ethambutol (Myambutol).
Ethambutol is an antibiotic used therapeutically in the treatment of tuberculosis that can affect trace-metal metabolism through its action as a chelating agent. Using a rodent model, Solecki et al. investigated the effects of ethambutol on tissue concentrations and balance of zinc, copper, iron, and manganese. They observed that ethambutol “produced significant decreases in heart copper, kidney zinc, plasma zinc, and liver copper and zinc not due to the associated reduced food intake.” No human trials or qualified case reports have appeared in the scientific literature to confirm this possible interaction in humans or determine its clinical significance.
Folic acid, folinic acid.
In addition to its availability as orally administered nutritional supplements, folic acid at doses greater than 1 mg is available in tablet and injectable forms with a prescription. Despite preliminary reports and unsubstantiated statements in the secondary literature indicating that folic acid administration can reduce blood levels of zinc, two reviews of folic acid safety concluded that such an adverse effect is improbable. Pending confirmation by more substantive evidence, physicians prescribing folic acid at supplemental levels or in prescription doses do not need to recommend compensatory coadministration of zinc. Nevertheless, monitoring serum/plasma levels and watching for clinical signs of zinc insufficiency (e.g., decreased smell/taste) would be prudent when folic acid is administered at higher therapeutic levels for an extended time; in cases where long-term zinc supplementation is added, low-dose copper may also be indicated.
Hydralazine (Apresoline).
The scientific literature provides very limited data on the potential interaction between zinc and hydralazine, and available research is convoluted by numerous confounding variables. Fjellner described a 58-year-old woman with long-standing hypertension and leg ulcers and mild joint involvement of 3 years, being treated for 6 years with hydralazine (30-200 mg/day) and propranolol (120-640 mg/day) as well as thyroxine and several other medications, who developed multisystemic manifestations of a lupus erythematosus–like syndrome within 1 week after introduction of oral zinc sulfate (200 mg three times daily). Clinical improvement, including healing of the oral ulcers and remission of the fever and abdominal distress, occurred on cessation of zinc intake. Notably, however, the patient's condition persisted until all the medications except thyroxine were discontinued. Clearly, attributing a multifactorial aggravation in a single case to an interaction between zinc and hydralazine would be speculative, at best, and extrapolating that to a generalized pharmacological phenomenon would be an ill-founded misrepresentation of the very limited data available, particularly since hydralazine is known to be capable of producing drug-induced lupus on its own. It is also notable that the dose of zinc in this case report was extremely high. Vigilance for similar case reports may be warranted so that a pattern of incidence and common risk factors might be elucidated.
Interferon alfa (Interferon alpha; Alferon N, Intron A, Roferon-A); combination drug: interferon alfa-2b and ribavirin (Rebetron).
Necrolytic acral erythema is a rare skin disorder categorized as a form of necrolytic erythema, along with acrodermatitis enterohepatica (congenital disorder of zinc metabolism), and apparently linked to infection with hepatitis C virus. Khanna et al. described the case of a “43-year-old black woman who presented with a 4-year history of tender, flaccid blisters localized to the dorsal aspect of her feet,” which was subsequently diagnosed as necrolytic acral erythema and chronic hepatitis C. Although her serum zinc level was normal, she was “successfully treated with interferon alfa-2b and zinc.” In a review of the literature on necrolytic acral erythema, these authors found four cases (of seven) “treated with variable success using oral zinc sulfate and amino acids, whereas 2 were successfully treated with interferon alfa,” even though “serum zinc levels were normal in all patients in whom they were measured.” The dose of oral zinc sulfate administered ranged from 60 to 440 mg per day and “was effective to varying degrees” in five (of eight) patients, including the authors’ original patient. In focusing on the interferon-zinc synergy they noted that in one case, “interferon alfa alone resulted in almost complete clearance of lesions,” whereas in the two other cases, “the addition of interferon alfa to oral zinc resulted in total clearance.” The authors interpreted the collective evidence from their case report and literature review to suggest that “interferon alfa alone may be sufficient to treat necrolytic acral erythema or may enhance the effect of oral zinc.” Further research appears to be warranted to investigate the mechanism(s) involved in this possible interaction, elucidate any relationship to zinc deficiency or faulty zinc metabolism as well as other forms of necrolytic erythema, and establish clinical guidelines, if confirmed to be effective.
Nystatin (Mycostatin, Nilstat, Nystex).
In a single in vitro study, Grider and Vazquez found that nystatin, a sterol-binding drug known to inhibit potocytosis, inhibited zinc uptake in both normal and acrodermatitis enteropathica (AE) fibroblasts. They noted that “reduced cellular uptake of zinc was associated with its internalization, not its external binding.” The authors concluded that “nystatin exerts its effect on zinc uptake by reducing the velocity at which zinc traverses the cell membrane, possibly through potocytosis,” and that “the AE mutation also affects zinc status by reducing zinc transport.” These preliminary findings, if confirmed by further research, suggest that individuals on nystatin therapy, especially for an extended period, may be at risk for zinc depletion and that zinc coadministration may be indicated; the potentially beneficial effects of zinc on immune function may provide added benefit, particularly in the presence of compromised zinc status.
An emerging body of evidence largely indicates that zinc in conjunction with an antioxidant network strategy, particularly one emphasizing lutein and anthocyanoside-rich plants such as bilberry (Vaccinium myrtillus),may prevent or slow the advance of macular degeneration. Research continues in this important area.
Numerous reports suggest that calcium at high doses (e.g., >1500 mg/day) may significantly impair zinc absorption. Animal research suggests interference with zinc uptake by intestinal mucosa due to counter–ion binding to mucus glycoproteins as a possible mechanism. However, this possible effect appears to be of limited clinical significance, especially if calcium is taken with food, which may improve the gastric environment. Further, the effect of calcium on gut pH, whether as supplement or as calcium-based antacids, can interfere with zinc absorption by altering gastric pH away from optimal (i.e., low) pH range, as noted in the discussion of Histamine (H 2 ) Receptor Antagonists.
In an early experiment, Pecoud et al. investigated the effect of foodstuffs on the absorption of zinc sulfate by administering single doses of zinc sulfate to healthy young volunteers, either in the fasting state or with various types of meals. They observed that “dairy products (milk and cheese) and brown bread decreased zinc absorption, as indicated by a significant drop in peak serum zinc levels.” Subsequently, however, other researchers have found that increases of calcium, within dietary sources or as calcium carbonate or hydroxyapatite, did not significantly alter zinc balance and retention in the presence of meals.
In a study involving nine patients on hemodialysis and 11 controls, Hwang et al. studied the effects of calcium carbonate and calcium acetate, both known phosphate binders, on intestinal zinc absorption by measuring 1-hour and 2-hour serum zinc levels after oral administration of 50 mg of elemental zinc as zinc gluconate, with or without concomitant administration of 2 g calcium carbonate (800 mg elemental calcium) or 3 g calcium acetate (750 mg elemental calcium). They observed that intestinal zinc absorption after an oral zinc challenge decreased in patients on hemodialysis with concomitant administration of calcium acetate, but calcium carbonate did not decrease intestinal zinc absorption in either group.
In contrast to these earlier studies, later research has used physiological doses of zinc and calcium more typical of the amounts found in meals. For example, in an experiment involving nine healthy female college-age students, Argiratos and Samman observed that the plasma zinc AUC after simultaneous ingestion of zinc with calcium carbonate and calcium citrate (600 mg elemental calcium) was significantly lower than that after ingestion of zinc alone, reflecting a 72% and 80% reduction, respectively, in zinc absorption. The authors concluded that the “decrease in zinc absorption following the ingestion of zinc with different forms of calcium suggests that an antagonistic competition occurred between the minerals and that elemental calcium is the inhibiting factor.”
In a trial involving 44 hemodialysis patients, Hwang et al. found that short-term and long-term uses of calcium acetate (containing 25.35 mmol elemental calcium daily) did not change hair and serum zinc concentrations over an 8-month period. The authors noted that even though daily calcium did “not significantly interfere with zinc absorption and storage” in hemodialysis (HD) patients, the “comparable hair zinc content in the presence of decreased serum zinc concentrations indicates that the metabolic processing of zinc in HD patients is different from that of normal individuals.”
Overall, the available data indicate that an antagonistic relationship between calcium and zinc may adversely affect zinc bioavailability with simultaneous intake in a fasting state, but that the presence of substantial food or separation of intake can minimize any such pharmacokinetic interaction. The resulting recommendation that patients ingest their zinc with a meal, but preferably not one high in phytates (e.g., grains, soy), or at least 2 hours away from calcium preparations is consistent with other known pharmacological principles and optimal clinical practices.
The complex interaction between these two pivotal minerals is well documented and generally agreed on but often oversimplified. Zinc significantly interferes with copper absorption and thus can cause copper deficiency or be therapeutic in the treatment of individuals with Wilson's disease. Zinc induces intestinal cell metallothionein, which binds copper and prevents its transfer into blood; eventually the intestinal cells die and slough, taking the trapped copper with them in the stool, thus preventing intestinal absorption of copper. However, the combined presence of these two minerals in Cu/Zn superoxide dismutase indicates that they do not relate only competitively. Such key complementary activity, along with the whole arena of metalloenzymes, is only beginning to become the subject of research with practical clinical significance.
Prolonged intake of supplemental zinc, particularly longer than 1 month, warrants compensatory copper supplementation, typically 1 to 3 mg daily, except for individuals with Wilson's disease or when the therapeutic strategy employs zinc as an anticopper agent. The typical recommended ratio of zinc to copper is 10:1 to 20:1, with relatively higher zinc allowable in some elderly patients, who, at least in the United States, tend to have a history of ingesting water carried through copper pipes, and who tend to have a diet higher in copper and lower in zinc. Baseline serum copper and zinc levels, although not necessarily reflective of various metabolic pools, can nevertheless be useful in guiding the relative dosing of these two minerals where appropriate. Copper preparations should be taken at least 2 hours apart from zinc preparations.
The luminal phase of zinc intestinal absorption may be mediated by low-molecular-weight substances, with amino acids being primary candidates for this role through the formation of complexes with zinc. A significant proportion of plasma zinc exists complexed with amino acids. Zinc absorption may be enhanced by concomitant intake of the amino acid L-cysteine concluded that. However, one study found that L-cysteine stimulates zinc uptake in rat but not in human erythrocytes. Notably, L-cysteine may also help mobilize and excrete copper. Some clinicians suggest that L-cysteine is a CNS excitotoxin with potentially damaging effects, but that coadministration with zinc may block such effects. Pending further research, this potential interaction is most accurately characterized as speculative.
See section in Theoretical, Speculative, and Preliminary Interactions Research.
Many clinicians experienced in natural medicine and integrative therapeutics place major importance on the phenomenon of excessive intestinal permeability, also known as dysbiosisor “leaky gut syndrome,” diagnosed by alterations in the differential absorption of lactulose and mannitol. This syndrome can occur in patients with Crohn's disease or other GI pathology and potentially in large segments of the population whose gut ecology has been disrupted by the adverse effects of antibiotics and other stressors on healthy intestinal flora. Probiotics and glutamine are among the core treatment elements typically used in therapeutic regimens to restore gut wall integrity and normal intestinal flora colonization.
Sturniolo et al. administered oral zinc sulfate (110 mg three times a day) for 8 weeks to 12 patients “with quiescent Crohn's disease who had been in remission for at least 3 months and had increased intestinal permeability on two separate occasions within the last 2 months.” They found that “the lactulose/mannitol ratio was significantly higher before supplementation than after,” and that during follow-up 12 months later, 10 patients “had normal intestinal permeability and did not relapse; of the remaining two who had increased intestinal permeability, one relapsed.” The authors concluded that their “findings show that zinc supplementation can resolve permeability alterations in patients with Crohn's disease in remission” and that “improving intestinal barrier function may contribute to reduce the risk of relapse in Crohn's disease.”
Histidine is involved with the regulation of zinc levels. Both zinc and L-histidine are known competitors of intestinal copper uptake, and concomitant L-histidine intake may enhance the absorption of zinc. Moreover, L-histidine can stimulate zinc uptake by erythrocytes. In a study investigating zinc-dependent cognitive function, Keller et al. found that coadministration of L-histidine during dietary zinc repletion improved short-term memory in zinc-restricted young adult male rats.
Interactions between iron and zinc appear to occur both during intestinal absorption and throughout the body after absorption. Iron and zinc may compete for absorption because of similarities in physicochemical properties and potentially shared absorptive pathways, such that bioavailability and therapeutic activity of both agents could potentially be reduced with simultaneous intake. Intestinal divalent metal transporter-1 (DMT1) has been proposed as a possible site, but others have noted that zinc is not transported by the DMT1. This possible pharmacokinetic interaction can be difficult to manage clinically because iron and zinc deficiencies occur together in various populations and may have to be addressed concurrently, especially among women and children in developing countries. In a review of literature investigating the interplay between iron and zinc at the level of enterocyte and neural tissues, Kordas and Stoltzfus reported complex and paradoxical findings but clear patterns of probability. Their in vitro research indicates that iron may inhibit zinc absorption in some cells at very high ratios of iron to zinc, but not vice versa. Consequently, they proposed “a shift in thinking about iron-zinc interactions from the level of enterocyte to other sites/systems in the body [such as the nervous system] that may be equally relevant for the outcome and interpretation of supplementation trials.”
Various studies have reported diverse interactions between zinc and iron, depending on forms, preparation, and doses administered; concomitant intake; protocol design; subject life phase (e.g., pregnancy); and trace-element status of subjects. Solomons observed that inorganic iron competed for absorption with zinc when given to adults in solution in ratios greater than two to one. However, iron did not significantly affect zinc absorption when they administered Atlantic oysters, providing 54 mg “organic” zinc (vs. inorganic zinc sulfate). Thus, “the evidence for competitive interaction of zinc and iron was strongest with nonheme iron and inorganic zinc.” In human experiments, Rossander-Hulten et al. compared the effect of zinc on iron absorption both in solution and in a hamburger meal and observed no inhibitory effect, “suggesting different pathways for the absorption of zinc and iron.” They did, however, find that an “intraluminal interaction may occur, because a fivefold excess of zinc to iron (15 mg Zn/3 mg Fe) reduced iron absorption by 56% when given in a water solution but not when given with a hamburger meal.” Nevertheless, they noted that “fractional iron absorption is strongly dose dependent.” Similarly, using a rodent model, Peres et al. demonstrated that inhibition of zinc absorption by iron depended on their ratio and the deficiency/repletion status of each mineral in the animals. “Between 2:1 and 5:1 a dose dependent inhibition of zinc absorption occurred and reached a plateau beyond this ratio. In iron deficient animals no changes in zinc uptake, mucosal retention and absorption compared to normal animals occurred at ratio 2:1.” Meadows et al. studied the oral bioavailability of zinc in nonpregnant adults before and 24 hours after 2 weeks of oral administration of iron and folic acid. They found that “bioavailability was greatly reduced, and the shape of the plasma curves suggested that this was due to impairment of the intestinal absorption of zinc.” The authors interpreted their findings as suggesting that “the reduced bioavailability of zinc occurs because of interelement competition in the bowel wall” and cautioned that this phenomenon “might induce zinc depletion.” O’Brien et al. reported that zinc absorption was significantly reduced in fasting pregnant Peruvian women administered inorganic iron or inorganic iron plus zinc, compared with nonsupplemented women. However, they also noted that plasma zinc concentrations were also lower in women administered only iron, compared with controls.
In contrast, other researchers observed smaller improvements in hemoglobin and serum ferritin concentrations in Indonesian children administered both iron and zinc than in children given iron alone. Similarly, Donangelo et al. found that concomitant zinc (22 mg daily as zinc gluconate and 100 mg iron daily as ferrous sulfate) can lower measures of iron status in nonanemic young women with low iron reserves. In reviewing the literature on interactive effects of iron and zinc on biochemical and functional outcomes in supplementation trials, Fischer Walker et al. concluded that “zinc supplementation alone does not appear to have a clinically important negative effect on iron status. However, when zinc is given with iron, iron indicators do not improve as greatly as when iron is given alone…. Although some trials have shown that joint iron and zinc supplementation has less of an effect on biochemical or functional outcomes than does supplementation with either mineral alone, there is no strong evidence to discourage joint supplementation.”
Zinc is often combined with other nutrients, including iron, in the prevention and treatment of nutritional deficits and resulting health problems among impoverished infants and children, especially in nonindustrial societies. In a longitudinal, double-blind, placebo-controlled trial, Muñoz et al. found that coadministration of zinc (20 mg/day), iron (20 mg/day), or the combination for 6 months improved indicators of vitamin A status, particularly higher plasma retinol and transthyretin, compared with placebo, in Mexican preschoolers.
Fortunately, analysis of these complex findings produces some clear and consistent clinical guidelines. The body of evidence indicates that clinically significant adverse pharmacokinetic interactions can be avoided by separating intake of iron and zinc by at least 2 hours, outside the context of meals, or minimized by ingesting the nutrients with a meal, particularly one containing meat, which tends to be rich in both iron and zinc. These guidelines are most important in individuals at risk for compromised nutrient status, of either mineral or generally, with particular concern in pregnant women being supplemented with iron and thus potentially increasing risk of adverse effects, including intrauterine growth retardation and congenital abnormalities related to exacerbated zinc deficiency.
Zinc may exert inhibitory effects on magnesium balance and magnesium absorption in humans. Separating oral intact by at least 2 hours will generally mitigate any impairment of bioavailability of either mineral.
See also Histamine (H 2 ) Receptor Antagonists and related Antacids and Gastric Acid–Suppressive Medications.
In experiments on competitive inhibition of iron absorption by manganese and zinc in humans, Rossander-Hulten et al. found significant differences in the effect of the two minerals on manganese absorption, both in solution and in a hamburger meal. They observed that manganese “inhibited iron absorption both in solutions and in a hamburger meal” and that “fractional iron absorption is strongly dose dependent.” Conversely, in “the same experiment with zinc, no inhibitory effect was observed, suggesting different pathways for the absorption of zinc and iron.” However, an “intraluminal interaction may occur, because a fivefold excess of zinc to iron (15 mg Zn/3 mg Fe) reduced iron absorption by 56% when given in a water solution but not when given with a hamburger meal.” Thus, although the impact of manganese on zinc absorption appears to be significantly less than on iron availability, separating oral intact by at least 2 hours will generally mitigate any impairment of bioavailability of either mineral.
N-acetylcysteine (NAC), particularly with high doses administered intravenously, as used clinically for acetaminophen poisoning, can complex with zinc, possibly increasing zinc absorption but also increasing urinary zinc excretion. Coadministration of zinc (and copper) may be prudent in individuals using NAC on a long-term basis.
Zinc absorption may be impaired in riboflavin deficiency. Supportive data are lacking to confirm this possible interaction.
Ashwagandha (Withania somnifera),boswellia (Boswellia serrata),turmeric (Curcuma longa).
In a randomized, double-blind, placebo-controlled, crossover study in 42 patients with osteoarthritis, Kulkarni et al. reported clinical efficacy, including a “significant drop in severity of pain … and disability score,” after treatment with a herbomineral formulation containing roots of Withania somnifera,the stem of Boswellia serrata,rhizomes of Curcuma longa,and a zinc complex (Articulin-F). Although the contribution of zinc to the clinical efficacy observed cannot be determined with this research design, further research through well-designed and adequately powered clinical trials may be warranted.
Bloodroot (Sanguinaria canadensis).
Several studies have investigated and supported a synergistic interaction between zinc and sanguinaria in the treatment of plaque, halitosis, and gingivitis.
Evening Primrose Oil (Oenothera biennis).
Weak evidence from preliminary research indicates that concomitant administration of zinc and evening primrose oil may be beneficial in the treatment if individuals diagnosed with attention deficit–hyperactivity disorder.
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