Antacids decrease the absorption of Tetracycline and Iron. Take Tetracycline 1 hour before or 2 hours after antacids and 2 hours before or 3 hours after Iron-containing preparations.
Antacids may decrease the absorption of orally administered Digoxin, or Indomethacin, Isoniazid, Quinolones (e.g., Ciprofloxacin, Ofloxacin), Ketoconazole. Doses of these drugs should be spaced as far apart as possible from doses of antacids.
Antacid-induced changes in urine pH increase urinary excretion and decrease blood concentration of salicylates such as Aspirin.
Antacid-induced increases in urine pH may decrease excretion of weakly basic drugs (e.g., Quinidine, Chlorpromazine, Propranolol, Diazepam) and increase excretion of weakly acidic drugs (e.g., Phenytoin, Pentobarbital, Warfarin).
Aluminum-Magnesium antacid combination is reported to increase the absorption of Dicumarol, Diazepam and Pseudoephedrine.
Magnesium and Aluminum Hydroxide administration may decrease the rate of Chlordiazepoxide absorption.
Antacids reduce the bioavailability of bisphosphonates (e.g., Alendronate, Etidronate, Risedronate).