Reduced GI absorption of tetracyclines. Increased blood quinidine levels. Al hydroxide: May reduce absorption of H
2 antagonists, atenolol, cefdinir, cefpodoxime, chloroquine, diflunisal, digoxin, bisphosphonates, ethambutol, fluoroquinolones, Na fluoride, glucocorticoids, indomethacin, INH, kayexalate, ketoconazole, lincosamides, metoprolol, phenothiazine neuroleptics, penicillamine, propranolol, Fe salts. Increased Al levels w/ citrates particularly in patients w/ kidney failure.