Calcium Carbonate: 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.
Calcium Gluconate: Co-admin of high calcium doses with thiazide diuretics may result in milk-alkali syndrome and hypercalcaemia. May potentiate digoxin toxicity. Decreases effects of calcium-channel blockers. Enhanced absorption with calcitriol (a vitamin D metabolite).
Vit C: Deferroxamine, hormonal contraceptives, flufenazine, warfarin, elemental iron, salicylates, warfarin, fluphenazine, disulfiram, mexiletine, vitamin B12.