Purpose: To review the recent literature on the efficacy of combined insulin and sulfonylurea therapy in patients with type 2 diabetes.
Data sources: Pertinent articles were obtained through an English-language MEDLINE search from 1979 to 1990 and from the references of these articles.
Study selection: We reviewed the studies in which patients with poorly controlled diabetes received insulin and a sulfonylurea agent and in which insulin treatment alone (usually given in conjunction with a placebo) was compared with insulin plus sulfonylurea therapy.
Data extraction: Pre- and post-treatment insulin doses, blood glucose levels, glycated hemoglobin values, C-peptide levels, and insulin levels were analyzed. Other data were analyzed separately.
Results of data synthesis: Data from similar trials were compared. Data from concurrent trials were analyzed separately from data derived from cross-over trials. Weighted mean fasting blood glucose levels, glycated hemoglobin levels, insulin dosage, and fasting C-peptide concentrations were determined for insulin plus placebo and insulin plus sulfonylurea agent groups for both types of studies. In concurrent trials, the weighted mean post-treatment glycated hemoglobin level was 11.1% after insulin plus placebo compared with 10.0% after insulin plus a sulfonylurea agent. In cross-over trials, the corresponding values were 10.6% and 9.8%.
Conclusions: Combination therapy with insulin and a sulfonylurea agent only slightly improved glycemic control in patients with type 2 diabetes. When a sulfonylurea agent was used, less exogenous insulin was needed, but fasting serum insulin levels were not different between the treatment groups. Such therapy did not produce nearly normal blood glucose concentrations and therefore should not be used in patients with poorly controlled type 2 diabetes receiving insulin.