Ferrous sulfate drug interactions

Antacids also have clinically significant drug interactions with tetracycline, ferrous sulfate, isoniazid, quinidine, sul-fonylureas, and quinolone antibiotics. Antacid-drug interactions are influenced by antacid composition, dose, dosage schedule, and formulation. 

Drug/Food interactions Administration of iron with food decreases the iron absorption by at least 50%. Administration of calcium and iron supplements with food can reduce ferrous sulfate absorption by 33%. If combined iron and calcium supplementation is required, iron absorption is not decreased if calcium carbonate is used and the supplements are taken between meals. 

Drug Interactions Various drugs can decrease T absorption. Drugs such as aluminum hydroxide, ferrous sulfate, sucralfate, and calcium carbonate should be separated from T administration by 1 to 2 hours. Bile acid sequestrants (cholestyramine and colestipol) must be separated from T by at least 4 hours and preferably 6 hours. CYP450 enzyme inducing drugs such as phenytoin, carba-mazepine, rifampin, and phenobarbital can increase T requirements. 

An established interaction of clinical importance. Avoid ferrous sulfate and other iron compounds while taking cefdinir. It is not yet known how far apart these drugs must be separated to avoid this interaction, but 3 hours improves the situation considerably even if it does not totally solve it. There is no information to suggest that other eephalosporins interact in this way. 

Studies have shown that colestyramine binds with iron, and in rats this was found to halve the absorption of a single 100-microgram dose of ferrous sulfate. Nobody seems to have checked on the general clinical importance of this in patients. Until more is known it would seem prudent to separate the dosages of the iron and colestyramine to avoid mixing in the gut, thereby minimising the effects of this possible interaction. The standard recommendation is to avoid other drugs one hour before or 4 to 6 hours after colestyramine. 

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