Transient effect of the combination of insulin and sulfonylurea (glibenclamide) on glycemic control in non-insulin dependent diabetics poorly controlled with insulin alone.

In a double-blind cross-over study we compared the effects of insulin plus glibenclamide, 5 mg twice daily, with insulin plus placebo during 8-week periods on metabolic parameters in 13 non-insulin dependent diabetic (NIDDM) patients poorly controlled with insulin alone. The combination therapy improved diabetic control as assessed by fasting blood glucose (p less than 0.001), 24-hour urinary glucose (p less than 0.01) and glycohemoglobin (HbA1) concentrations (p less than 0.05 at week 12). The effect tended to cease with time. Significantly higher C-peptide values were found during combination treatment than during insulin-placebo (p less than 0.01) and the changes in fasting C-peptide concentrations correlated positively with the changes in HbA1 concentrations (r = 0.56, p less than 0.05). There was no difference in glucagon concentrations, insulin binding to erythrocytes or insulin sensitivity between the two study periods. Neither did the combination therapy influence blood lipids significantly. The present study shows that the combination of insulin and glibenclamide may be of limited value in the treatment of NIDDM patients poorly controlled with insulin alone. However, thus far the long-term results are uncertain. In the absence of significant effects on insulin binding and insulin sensitivity, the improved diabetic control seems to be explained, at least partly, by glibenclamide-induced stimulation of insulin secretion.