Propranolol does not inhibit sulphonylurea-stimulated insulin secretion in patients with non-insulin dependent diabetes mellitus

In a double-blind cross-over trial we compared the effects of placebo and propranolol on iv tolbutamide and oral glipizide-stimulated insulin secretion in 10 noninsulin dependent diabetics. The patients were randomly allocated for 2 weeks treatment with placebo and propranolol 80 mg twice daily. At the end of each period an iv tolbutamide test and an oral glipizide-glucose-test were performed. Tolbutamide-stimulated insulin secretion was not affected by propranolol. There was no change in blood glucose levels during the iv tolbutamide test (IVTT), which excluded an effect of blood glucose on insulin secretion. During the oral glipizide-glucose challenge propranolol decreased blood glucose at 60 min (P < 0.01) and increased C-peptide at 0 min (P < 0.01) and 30 min (P < 0.05) compared with placebo. In contrast to earlier results obtained in animals and healthy subjects propranolol does not inhibit insulin- or C-peptide responses to sulphonylurea in patients with non-insulin dependent diabetes mellitus.