Effects of metoprolol and propranolol on glucose tolerance and insulin secretion in diabetes mellitus.

Twenty-two hypertensive diabetic patients were admitted to a double-blind, within-patient study, and treated with propranolol 80 mg and metoprolol 100 mg twice daily for 4 weeks according to a cross-over design. Dosages of the two drugs such as to induce comparable cardiovascular effects, did not induce relevant changes of fasting blood glucose levels in patients receiving the oral hypoglycaemic agent glibenclamide (group 1), insulin (group 2) or diet alone (group 3). Glucose tolerance, assessed with a 75 g oral load, was however decreased by propranolol, and not by metoprolol in the glibenclamide-treated group. Glucose-induced insulin secretion was reduced by propranolol and not by metoprolol both in the group treated by diet alone and in the glibenclamide-treated group. It is concluded that cardioselective metoprolol seems to be more suitable than the non-selective propranolol in the treatment of arterial hypertension in diabetic subjects, particularly when sulfonylureas are being used as hypoglycaemic agents.