Oral verapamil does not affect glucose tolerance in non-diabetics.

Verapamil, a calcium antagonist used to treat angina pectoris, inhibits insulin release in vitro and, when administered intravenously to humans, decreases glucose tolerance. Oral verapamil, 120 mg/day for 1 week increasing thereafter to 240 mg/day in divided doses, was given to nine non-diabetic patients with angina pectoris for 4 weeks. The glucose and insulin responses to a standard glucose load showed no significant difference before and after verapamil. Oral verapamil in the doses used in this study had no significant effect on glucose tolerance in non-diabetics.