Effect of tolbutamide on plasma catecholamine in insulin dependent diabetics

In 4 cases of insulin dependent diabetics, blood levels of glucose, C-peptide reactivity (CPR), free fatty acid, and catecholamines were followed after the intravenous tolbutamide response test. Plasma CPR was low and did not respond to tolbutamide injection, and blood levels of glucose and free fatty acid did not change during the test. Fifteen min after the tolbutamide injection, plasma epinephrine plus norepinephrine and norepinephrine levels fell to 87.5% and 67.4% of the initial values, respectively. These results suggest that decrease in the blood glucose and free fatty acid levels usually observed after tolbutamide injection is not the direct action of drug, but is secondary to insulin secretion, and tolbutamide-induced decrease in catecholamines may contribute to the secretion of insulin from the pancreatic beta-cells.