Iron : Interactions with Drugs and Dietary Supplements

by MedlinePlus

(Page 4 of 4)

Interactions with Drugs

Acetohydroxamic acid (AHA, Lithostat®): AHA is prescribed to decrease urinary ammonia, and may help with antibiotics to work or help with other kidney stone treatment. Use with iron supplements may cause either medicine to be less effective.

Allopurinol (Zyloprim®): Allopurinol, a medication used to treat gout, may increase iron storage in the liver and should not be used in combination with iron supplements.

Aminosalicylic acid: Aminosalicylic acid (para-aminosalicylic acid, PAS, Paser) may cause a malabsorption syndrome (weight loss, iron and vitamin depletion, excessive fat in the stools (steatorrhea). A qualified healthcare provider should be contacted immediately if any of these symptoms are experienced.

Antacids: Antacids may reduce iron absorption. Antacids can reduce absorption of iron from supplements by 30% to 40%, and reduced efficacy has occurred occasionally. Clinically significant effects are unlikely with adequate dietary iron intake. However, it is recommended to avoid antacids or separate the doses of antacids and iron.

Aspirin, Nonsteroidal Anti-inflammatory Drugs (NSAIDs): Aspirin and NSAIDs can cause mucosal damage and bleeding throughout the gastrointestinal (GI) tract. Chronic blood loss associated with long-term use of these agents may contribute to iron deficiency anemia. Since iron supplements may also irritate the GI tract, patients should not use them concurrently with NSAIDs unless recommended by a physician. Iron rich food intake may be advised as an alternative.

Bisphosphonates: Iron can decrease absorption of prescription drug bisphosphonates by forming insoluble complexes. Bisphosphonates include alendronate (Fosamax®), etidronate (Didronel®), risedronate (Actonel®), and tiludronate (Skelid®). Doses of bisphosphonates should be separated by at least two hours from doses of all other medications, including supplements such as iron.

Chloramphenicol (Chloromycetin®): Chloramphenicol can reduce the response to iron therapy in iron deficiency anemia.

Cholestyramine (Questran®), Colestipol (Colestid®): Cholestyramine and colestipol may bind iron in the gut, reducing its absorption. Clinically significant iron deficiency induced by these drugs has not been reported, and supplements are not likely to be needed. If taking iron supplements for other causes of deficiency, it is recommended that the iron and cholestyramine or colestipol doses be separated by at least four hours.

Desferrioxamine (DFO): DFO is an iron-chelating drug that lowers iron levels.

Dimercaprol: Iron supplements and dimercaprol may combine in the body to form a harmful chemical.

EPO-R: Bone marrow iron deposits have been shown to decrease significantly in patients on EPO-R.

Fluoroquinolone antibiotics: Iron decreases the absorption of fluoroquinolones. Fluoroquinolones include ciprofloxacin (Cipro®), levofloxacin (Levaquin®), ofloxacin (Floxin®), and others. It is recommended to take these antibiotics at least two hours before or two hours after iron-containing supplements.

H2-blockers: Gastric acid is important for the absorption of iron, particularly dietary non-heme (plant-derived) iron. Adequate dietary iron intake is recommended when taking H2 blockers like cimetidine (Tagamet®), ranitidine (Zantac®), famotidine (Pepcid®), or nizatidine (Axid®). Iron supplements are not usually required unless they are being used for another indication.

Levodopa (Sinemet®): There is some evidence in healthy people that iron forms chelates with levodopa, reducing the amount of levodopa absorbed by around 50%. Until further research is available, separate doses of levodopa and iron as much as possible.

Levothyroxine (Levoxyl®, Synthroid®): Iron can decrease the absorption and efficacy of levothyroxine by forming insoluble complexes in the gastrointestinal tract. It is recommended that levothyroxine and iron doses be separated by at least two hours.

Methyldopa (Aldomet®): Iron can decrease absorption of methyldopa, resulting in increases in blood pressure. It is recommended that methyldopa and iron doses be separated by at least two hours.

Mycophenolate Mofetil (CellCept®): Oral iron supplements markedly reduce absorption of mycophenolate mofetil. It is recommended that iron be taken four to six hours before, or two hours after mycophenolate mofetil.

Pancreatic enzymes, pancrelipase, pancreatin:There is some evidence that pancreatic enzyme supplements (such as Cotazym®, Creon®, Pancrease®, Ultrase®, Viokase®), can reduce iron absorption, possibly by binding iron or altering pH. Clinical significance is unlikely, except in people with cystic fibrosis who need pancreatic enzyme supplements for prolonged periods, and have other factors contributing to iron deficiency. Iron status should be monitored by a qualified healthcare provider.

Penicillamine (Cuprimine®, Depen®): Oral iron supplements can reduce absorption of penicillamine by 30% to 70%, probably due to chelate formation. Efficacy of penicillamine is reduced in Wilson's disease; the clinical significance in people with rheumatoid arthritis (RA) has not been determined. Patients should be advised to take penicillamine at least two hours before or after iron-containing supplements.

Proton Pump Inhibitors (PPIs): Gastric acid is important for the absorption of iron, particularly dietary non-heme (plant-derived) iron. However, long-term treatment, up to 12.5 years, with proton pump inhibitors (such as esomeprazole (Nexium®), lansoprazole (Prevacid®), omeprazole (Prilosec®), rabeprazole (Aciphex®), pantoprazole (Protonix®, Pantoloc®) has not been associated with iron depletion or anemia in people with normal iron stores. Maintaining adequate dietary iron intake is recommended.

Tetracycline antibiotics: Concomitant use can decrease absorption of tetracyclines by 50% to 90%. Patients should be advised to take tetracyclines at least two hours before or after iron-containing supplements. Some of these drugs include doxycycline (Vibramycin®), minocycline (Minocin®), tetracycline (Achromycin®), and others.

Interactions with Herbs and Dietary Supplements

Acacia: Acacia forms an insoluble gel with ferric iron. Clinical significance is unknown.

Calcium: Calcium supplements have been shown to inhibit absorption of iron supplements when taken with food. Calcium inhibits the absorption of dietary heme- and non- However, in people with adequate iron stores, this does not appear to be clinically significant. If at risk for iron deficiency, it is recommended to take calcium supplements at bedtime, instead of with meals, to avoid inhibiting dietary iron absorption.

Copper: Copper metabolism may be altered by iron supplements, but the clinical importance of this observation is unknown.

Organic acids:Citric, malic, tartaric, and lactic acids have some enhancing effects on nonheme iron absorption.

Phytic acid (phytate):Phytic acid is present in legumes, grains, and rice and is an inhibitor of nonheme iron absorption. Small amounts of phytic acid (5 to 10mg) can reduce nonheme iron absorption by 50%. The absorption of iron from legumes, such as soybeans, black beans, lentils, mung beans, and split peas, has been shown to be as low as 2%.

Polyphenols: Polyphenols, found in some fruits, vegetables, coffee, tea, wines, and spices, can markedly inhibit the absorption of nonheme iron. This effect is reduced by the presence of vitamin C.

Riboflavin (vitamin B2): Riboflavin supplements may improve the hematological response to iron supplements in some people with anemia.

Selenium: Based on preliminary data, iron may decrease selenium levels. Further research is needed to confirm these results.

Soy: Soy protein reduces absorption of dietary non-heme (plant-derived) iron, probably due to binding of iron by phytate and calcium present in soy. Fermented soy products seem to inhibit of iron absorption less.

Vitamin A,Beta-carotene: Vitamin A appears to be involved in mobilizing iron from tissue stores for delivery to developing red blood cells in the bone marrow. Vitamin A may also be involved in the differentiation and proliferation of blood stem cells in the bone marrow, and in the synthesis of erythropoietin. Preliminary evidence also suggests that vitamin A and beta-carotene may enhance non-heme iron absorption from iron-fortified wheat and corn flour, and rice. It is unlikely that vitamin A supplements would have significant effects on iron status in people without vitamin A deficiency.

Vitamin C (ascorbic acid): The amount of vitamin C in the diet is a factor in dietary iron absorption and iron status. Vitamin C can counteract the effects of substances, which inhibit iron absorption. Supplemental or dietary vitamin C improves absorption of supplemental or dietary non-heme (plant-derived) iron ingested at the same time. Taking a vitamin C supplement to improve absorption of dietary or supplemental iron probably is not necessary for most people, especially if their diet contains adequate amounts of vitamin C. One study concludes that the addition of ascorbic acid increased fractional iron absorption from ferric pyrophosphate significantly, but to a lesser extent than from FeSO4.

Vitamin E: Use of oral iron preparations in premature infants with low serum vitamin E levels may cause hemolysis and hemolytic anemia. Vitamin E deficiency should be corrected before administering supplemental iron.

Zinc: Iron may decrease zinc absorption but there does not seem to be a clinically significant interaction between dietary iron and zinc, or between supplemental iron and zinc dietary sources.

Interactions with Food

Coffee and tea: These beverages can reduce absorption of both dietary and supplemental iron when taken at the same time. This is likely due to binding of iron in the gut by polyphenols/tannins in tea and coffee.

Dairy products: Calcium in dairy products such as milk and cheese can reduce the absorption of dietary and supplemental iron. It is recommended that iron supplements be taken with a meal that is relatively low in dairy products when possible.

Juice: Preliminary study shows that a small supplement of iron is better absorbed when given with to infants with juice than with cow's milk.

Meat, fish, poultry: Animal protein provides highly absorbable heme iron and enhances absorption of non-heme iron.

Interactions with Labs

Desferrioxamine mobilization test in hemodialysis patients: Iron supplements may significantly reduce the basal serum Al and peak Al in DFO mobilization test, without significant change of the mean delta Al.

Guaiac test: Iron may cause a false-positive reading for occult fecal blood. However, the benzidine test for occult fecal blood is not likely to be affected.

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