As a precaution for antacids, in order to minimise the risk of interactions affecting pharmacokinetics of concomitantly administered products, drug administrations should be separated by approximately 2 to 3 hours.
Magnesium salts reduce the absorption of a number of other drugs taken concomitantly. These include ACE inhibitors (captopril, enalapril, and fosinapril), antibacterials and antifungals (azithromycin, cefaclor, cefpodoxime, isoniazid, itraconazole, nitrofurantoin, rifampicin, tetracyclines, ketoconazole and the quinolone group of antibacterials); antivirals (atazanavir, fosamprenavir, tipranavir); antihistamines (fexofenadine); bisphosponates, corticosteroids (deflazacort); digoxin, dipyridamole, diflunisal, antiepileptics (gabapentin and phenytoin), ulcer healing drugs (lansoprazole); levothyroxine, mycophenolate, iron preparations, lipid regulating drugs (rosuvastatin); antipsychotics (sulpiride, phenothiazines), chloroquine, hydrochloroquine, proguanil, and penicillamine. Concomitant use with sodium polystyrene sulphonate may produce metabolic alkalosis. Alkaline urine due to some antacids increases excretion of aspirin. Antacids should be avoided with nilotinib.
Antacids possibly reduce absorption of bile acids.
Urine alkalinisation secondary to administration of magnesium hydroxide may modify excretion of some drugs; thus, increased excretion of salicylates has been seen.