Combined metformin and insulin therapy for patients with type 2 diabetes mellitus

This study was undertaken to assess the effects of combined treatment with insulin and metformin in patients with type 2 diabetes mellitus in whom dietary measures, weight control, and oral antihyperglycemic therapy had failed.

Insulin resistance in peripheral tissues, increased hepatic gluconeogenesis, and impaired insulin secretion are the underlying factors in the development of type 2 diabetes. Metformin is a biguanide antihyperglycemic agent that increases peripheral insulin sensitivity, reduces hepatic gluconeogenesis, and decreases intestinal glucose absorption.

Thirty-one patients (24 women, 7 men; mean age, 61.8 years; mean body mass index [BMI], 28.0 kg/m2) were enrolled in this randomized, double-blind, 2-way, crossover, placebo-controlled study. Patients with type 2 diabetes who were treated previously with insulin or oral hypoglycemic agents and who had a glycosylated hemoglobin (HbA1c) level >9% or a fasting blood glucose level >8 mmol/L were included. Patients who were being treated with oral agents were switched to insulin therapy and required to maintain stable blood glucose control for 2 months prior to randomization. Patients received insulin plus either metformin 1,700 mg/d or placebo for 5 months, followed by a 2-month washout period, and were then crossed over to the other treatment arm for 5 months of additional treatment (total treatment period: 12 months).

Thirty patients completed the study; 1 patient withdrew early because of hypoglycemia. Compared with placebo, metformin produced significant reductions from overall baseline in mean daily insulin dose requirement (-8.69 units (17.2%], P < 0.001), HbA1c level (-0.74 [9.9%], P = 0.005), serum fructosamine level (-44.40 micromol/L, P = 0.026), 24-hour blood glucose profile (P = 0.008), and total cholesterol level (-0.42 mmol/L, P = 0.005). No treatment effects were observed on body weight, blood pressure, serum high-density lipoprotein cholesterol levels, or serum triglyceride levels. There was no correlation between BMI and reduction in HbA1C. No major side effects were reported.

Combination therapy with metformin and insulin improves glycemic control and reduces insulin requirements. with no major side effects, in patients with type 2 diabetes and may improve the risk profile in this patient population.