Ferrous sulfate Antacids

Because fluoroquinolones have a wide therapeutic index and dose-dependent toxicity, routine drug monitoring is not indicated. Monitoring fluoroquinolone concentration is indicated in renal failure, which wfll cause fluoroquinolones to accumulate. Optimal response occurs when serum concentration exceeds 1.5 Llg/mL. Activity is maintained as long as the trough concentration is >0.2flg/mL. Coadministration with antacids, ferrous sulfate, food, or sucralfate reduces absorption by 30% to 60%. Co-administration with morphine reduces absorption by >50%. 

If ciprofloxacin, a member of the fluoroquinolones family, is prescribed, then it should be given two hours before the patient is given antacids, ferrous sulfate, or sucralfate because these medications lower the absorption of ciprofloxacin. 

Shiba K, Sakai 0, Shimada J, Okazaki 0, Aoki H, Hakusui H. Effects of antacids, ferrous sulfate, and ranitidine cn absoiptiai of DR-3355 in humans. Antimicrob Agents... 

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. 

The oral dosage for rapidly excreted tetracyclines, equivalent to tetracycline hydrochloride, is 0.25-0.5 g four times daily for adults and 20-40 mg/kg/d for children (8 years of age and older). For severe systemic infections, the higher dosage is indicated, at least for the first few days. The daily dose is 600 mg for demeclocycline or methacycline, 100 mg once or twice daily for doxycycline, and 100 mg twice daily for minocycline. Doxycycline is the oral tetracycline of choice because it can be given as a once-daily dose and its absorption is not significantly affected by food. All tetracyclines chelate with metals, and none should be orally administered with milk, antacids, or ferrous sulfate. To avoid deposition in growing bones or teeth, tetracyclines should be avoided in pregnant women and children less than 8 years of age. 

Tetracyclines, as broad-spectrum antibiotics, are the drugs of choice in treating Mycoplasma pneumoniae infections. Most tetracyclines are absorbed to various degrees (30 to 100%) from the gastrointestinal tract, primarily from the stomach and upper small intestine. The absorption of tetracyclines is hindered by milk and milk products, by numerous antacids such as aluminum hydroxide, sodium bicarbonate, and calcium carbonate, and by iron preparations such as ferrous sulfate. Therefore, these and similar substances should not be administered orally together with tetracycline (Figure 3.4). 

Tetracyclines Dairy products high in calcium ferrous sulfate or antacids Impaired absorption of tetracycline... 

Osman MA, Patel RB, Schnna A, Snndstrom WR, Welling PG. Reduction in oral penicillamine absorption by food, antacid, and ferrous sulfate. CUn Pharmacol Ther 1983 33(4) 465-70. 

Pregnant women require an increased an amount of iron, but they need to avoid a megadose in the first trimester because it might cause birth defects. Larger doses of iron are necessary in the second and third trimester. Iron is absorbed in the intestine where it enters plasma as heme or is stored as ferritin in the liver, spleen, and bone marrow. Food, the antibiotic tetracychne, and antacids decrease absorption up to 50% of iron. However, the patient should take iron with food to avoid GI discomfort. Vitamin C may slightly increase iron absorption. Iron toxicity is a serious cause of poisoning in children. Toxicity can develop with as few as 10 tablets of ferrous sulfate (3g) taken at one time—and can be fatal within 12 to 48 hours. 

B. Several drugs (eg, antacids and ferrous sulfate) and food can substantially reduce gastrointestinal absorption of penicillamine. 

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