Postmarketing drug surveillance revealed the occurrence of hypoglycemia associated with the use of disopyramide phosphate (Norpace) for the control of ventricular arrhythmias. The data obtained suggest that elderly patients or those with impaired hepatic or renal function may be more at risk of developing hypoglycemia while taking disopyramide. In a clinical study, nine healthy male volunteers were dosed with disopyramide to steady-state concentration. Comparison of the glucose levels during periods of fast, when the presence of food did not present a confounding factor, suggested that disopyramide may have a glucoregulatory effect in humans. A placebo-controlled clinical study, conducted in 11 healthy, male subjects, demonstrated that disopyramide evoked a small, but statistically significant, decrease in glucose levels during both the fed and fasted state. None of the classical signs or symptoms associated with hypoglycemia were noted during either of these clinical studies.