A retrospective chart review of uncontrolled use of metformin as an add-on therapy in type 2 diabetes.

The hyperglycemia, hyperinsulinemia, insulin resistance, and obesity syndrome associated with type 2 diabetes can have debilitating consequences. The biguanide metformin has a mechanism of action that is complementary to those of insulin and the sulfonylureas, suggesting that combination therapy that includes metformin may result in improved glycemic control. The purpose of this retrospective chart review was to determine the effects of adding metformin in an uncontrolled fashion to existing therapy in obese patients with type 2 diabetes who had suboptimal glycemic control and insulin resistance. For the review, the records of 124 patients were divided into two groups: group 1 included 71 patients who were taking insulin with or without a sulfonylurea, and group 2 consisted of 53 patients who were taking a sulfonylurea alone. Metformin was added to patients' existing therapy in conjunction with downward titration of the sulfonylurea and insulin doses. A retrospective chart review was conducted at the end of 6 months for group 1 and at the end of 12 months for group 2 to determine the change from baseline in measures of diabetes control (ie, insulin and sulfonylurea dose, glycated hemoglobin [Hb A1c] value, body mass index [BMI], and lipid profiles). In group 1, the mean insulin dose decreased from 46.4 U/d at baseline to 6.1 U/d at the end of follow-up. Eighty-three percent of the patients were able to discontinue insulin therapy completely. Similarly, group 2 had statistically significant reductions in mean sulfonylurea dose. Both groups also achieved statistically significant reductions in Hb A1c, BMI, and total cholesterol level. The addition of metformin to treatment with insulin or sulfonylureas, either alone or in combination, significantly improved glycemic control and cholesterol levels and promoted weight loss in obese type 2 diabetic patients with insulin resistance. Less than 5% of patients reported mild, transient gastrointestinal side effects, none of which required cessation of metformin therapy. Five patients discontinued metformin due to lack of efficacy.