The effect of nicardipine on glucose and drug-stimulated insulin secretion in normal volunteers.

The effect of nicardipine on insulin secretion was examined in two double-blind, randomised, cross-over, placebo-controlled studies in normal volunteers. In the first study, the effect of acute dosing (via an intravenous infusion of 5 mg h-1 for 3 h) on the glucose, insulin, hormonal, and intermediary metabolite responses to an intravenous glucose tolerance test was determined in six healthy male volunteers. In the second study, the glucose, insulin, and C-peptide responses to intravenous tolbutamide (200 mg) was determined in another six male volunteers after oral dosing with nicardipine 30 mg three times daily for 1 week. A relative increase in insulin secretion was the principal finding of the first study. No other response was affected significantly. No significant differences between the nicardipine- and placebo-treated groups were noted in the insulin, glucose, and C-peptide measurements of the second study. In conclusion, treatment with nicardipine does not appear to impair insulin secretion in response either to an intravenous glucose load or intravenously administered tolbutamide.