Potentiated hypoglycaemic effect w/ aspirin, NSAIDs, phenylbutazone, clofibrate, sulfonamides, coumarin anticoagulants, cimetidine, imidazole antifungals, MAOIs. Diminished hypoglycaemic effect w/ rifampicin, barbiturates, phenytoin, alcohol, thiazide diuretics, dizoxide, glucocorticoids, estrogens or sympathomimetics. Early symptoms of hypoglycaemia may be masked by β-adrenoreceptor-blocking drugs eg, propranolol.