Metformin HCl is contraindicated in patients with renal impairment and liver failure because of an increased risk of hypoglycemia. Renal impairment may also predispose patients to lactic acidosis. Regular renal and hepatic monitoring is essential.
Drug Interactions involve drugs also excreted by the renal tubular pathway (e.g. amiloride, cimetidine, digoxin, morphine, procainamide, quinidine, vancomycin, trimethoprim). Cimetidine may increase Metformin levels by up to 50%.