To the Editor.
—The concentration of extracellular calcium ions influences insulin release from the pancreatic beta cells.1 Calcium antagonists acutely inhibit in vitro and in vivo the glucose- and sulfonylurea-induced insulin release, apparently by interfering with calcium entry into the beta cell.2,3 The long-term effects of verapamil administration on the normal pancreatic beta cell have not been defined. Therefore, we determined the basal blood glucose concentrations (by the glucose oxydase method) in a double-blind study of 28 nondiabetic subjects receiving either a placebo or verapamil in a dosage of 80 mg three times a day as treatment of chronic atrial fibrillation, as previously described.4 The basal blood glucose concentration was measured before the double-blind period, at the end of two weeks of treatment with a placebo, and two weeks after treatment with verapamil and was determined again at the end of seven months of treatment with verapamil.
Lang R, Klein HO, Shapiro MS, Kaplinsky E. Verapamil Therapy and Blood Glucose Concentration. Arch Intern Med. 1981;141(12):1724. doi:10.1001/archinte.1981.00340130162048