Glipizide: Decreased effect with beta-blockers, cholestyramine, hydantoins, thiazide diuretics and urinary alkalinizers.
Metformin: Additive effect with sulphonylureas. Antagonistic effects with diuretics, corticosteroids, phenothiazines, thyroid products, oestrogens, oral contraceptives, phenytoin, nicotinic acid, sympathomimetics, Ca channel blockers and isoniazid.
Potentially Fatal: Glipizide: Increased glipizide levels and effects with fluconazole, gemfibrozil, ketoconazole, NSAIDs, pioglitazone and sulfonamides. Increased hypoglycaemic effects with H2 antagonists, anticoagulants, androgens, cimetidine, salicylates, tricyclic antidepressants, probenecid, MAOIs, methyldopa, digitalis glycosides and urinary acidifiers.
Metformin: Lactic acidosis with alcohol and potentiation of hypoglycaemic effect. Cimetidine and furosemide may increase plasma-metformin levels. Drugs eliminated via renal tubular secretion may increase metformin levels.