Co-administration with thiazide diuretics or vit D may lead to milk-alkali syndrome and hypercalcaemia. Decreased absorption with corticosteroids. Decreases absorption of tetracyclines, atenolol, iron, quinolones, alendronate, Na fluoride, Zn and calcium-channel blockers. Enhances cardiac effects of digitalis glycosides and may precipitate digitalis intoxication.