<p>Potassium-depleting diuretics increase the effects of digitalis. Calcium particularly if administered rapidly by the intravenous route, may produce serious arrhythmia in digitalized patients. Quinidine, verapamil, amiodarone, propafenone, indomethacin, itraconazole, alprazolam, spironolactone, erythromycin, clarithromycin (and possibly other macrolide antibiotics) and tetracycline increase digoxin serum level. Besides antacids, kaolinpectin, sulfasalazine, neomycin, penicillamine, calestipol, metoclopramide, rifampin may interfere with intestinal absorption of digoxin resulting low serum concentrations of the drug.</p>