Plasma insulin and glucose levels in maturity onset diabetics treated with chlorpropamide

19 diabetic patients taking various doses of chlorpropamide were studied throughout a normal day. Plasma chlorpropamide levels were related to the daily dose of the drug and were relatively constant throughout the day. Blood glucose concentration was highest and the plasma insulin concentration lowest in patients taking the largest dose of chlorpropamide. Patients on a small daily dose of chlorpropamide were well controlled and had higher than normal insulin levels. --12 patients were restudied 10 days after stopping chlorpropamide. Although diabetic control deteriorated in all patients, plasma insulin concentration did not change significantly. This suggests that the long-term hypoglycaemic action of chlorpropamide is not dependent on an effect on the concentration of insulin in peripheral venous blood.