Insulin-metformin combination therapy in obese patients with type 2 diabetes

The aim of the study was to evaluate the effects of insulin-metformin combination therapy compared to insulin monotherapyin obese, insulin-requiring patients with type 2 diabetes mellitus. Eighteen patients uncontrolled on > or = 70 U/day of insulin monotherapy were investigated in this prospective, open-label study. Patients continued their previous insulin and dietary regimens for 4 weeks, after which metformin was added with doses titrated to achieve a fasting plasma glucose (FPG) < 7.8 mmol/l or until the maximum daily dose was reached. Insulin-metformin combination therapy was continued for an additional 8 weeks. Insulin-metformin combination therapy resulted in a significant decrease in glycated hemoglobin values with a final mean reduction of 1.5% +/- 1.2% (p = 0.001). FPG decreased significantly (p < 0.005) by week 4 of insulin-metformin therapy, but the change was not statistically significant by week 12, and daily insulin requirements were significantly reduced during combination therapy (p < 0.05). These results suggest that in obese patients with type 2 diabetes mellitus receiving > or = 70 U of daily insulin, the addition of metformin leads to improved glycemic control with lower daily doses of insulin and without adverse effects.