The influence of glipizide on early insulin release and glucose disposal before and after dietary regulation in diabetic patients with different degrees of hyperglycaemia.

An early defect in subjects with non-insulin-dependent diabetes mellitus (NIDDM) and the preceding phase of impaired glucose tolerance (IGT) is a reduction in early insulin release and hence a prolonged elevation of postprandial blood glucose. We therefore assessed whether a rapidly acting sulphonylurea (glipizide 5 mg 0.5 h before a test meal) could correct these disturbances in 38 IGT/NIDDM subjects, whose early insulin release and postprandial blood glucose elevations remained unimproved after 10 weeks of dietary regulation. We also assessed whether the efficacy of glipizide was dependent upon the ambient blood glucose concentration, and if early systemic availability of the drug was important for the blood glucose lowering effect. A single dose of glipizide normalized early insulin release and hence reduced the postprandial blood glucose increase that was not lowered by dietary regulation. The efficacy of glipizide was dependent upon the early systemic availability of the drug, but early systemic availability and efficacy were independent of the extent of blood glucose elevation, at least within a range of 6-12 mmol.l-1 of fasting blood glucose.