Influence of Oral Verapamil on Glucoregulatory Hormones in Man*

We evaluated the effect of treatment with placebo or verapamil (320 mg/day) for 2 weeks on glucose-induced insulin secretion and hypoglycemia-stimulated counterregulatory hormone secretion in hypertensive patients. Verapamil treatment was associated with a significant reduction in diastolic blood pressure (P = 0.02 vs. placebo). During a hyperglycemic clamp (plasma glucose raised 125 mg/dl above basal level) maintained for 90 min, plasma insulin increased 4- to 5-fold (early) and then to values 8- to 10-fold above baseline (late). These increments were identical during placebo or verapamil treatment. The rates of glucose metabolized during each study also were similar, suggesting that no significant change in insulin action occurred during drug treatment. When plasma glucose was allowed to decline precipitously from hyperglycemic levels (220 mg/dl) to nadirs ranging from 42-77 mg/dl, plasma concentrations of glucagon, cortisol, epinephrine, and norepinephrine all increased; however, no consistent differences in the counter-regulatory hormone responses could be attributed to verapamil therapy. We conclude that physiologically effective drug concentrations of verapamil capable of influencing blood pressure do not have a significant effect on secretion of glucoregulatory hormones in man.