[Body mass index, blood lactate and therapeutic effectiveness of metformin in type II diabetes mellitus].

Obese type II diabetic patients are often treated with metformin after full doses of sulfonylureas or insulin fail to achieve a satisfactory metabolic control. Clinical practice has often indicated that metformin has little effect on normal weight type II diabetics. The effectiveness of metformin vs placebo was evaluated in a double blind cross-over study on 53 type II diabetic patients with unsatisfactory glycaemic control. The patients were divided into two groups-the sulfonylurea-treated (S) and the insulin treated (I). Each group was then subdivided into three classes: 1) normal weight [BMI less than 25], 2) overweight [BMI 25-30] and 3) obese [BMI greater than 30]. Metformin did not modify body weight, plasma lipids or insulin profiles. Blood lactate increased slightly but only occasionally reached statistical significance. Metformin's antidiabetic activity was not influenced by the basal treatment (S or I) of the diabetics but was strongly linked to the degree of adiposity. Indeed both plasma glucose and HbA1 remained almost unchanged in normal weight patients. In the overweight and in the obese metformin significantly improved glycaemic profiles and reduced HbA1 levels. These results confirm clinical experience indicating that some degree of adiposity is a necessary prerequisite for metformin efficacy in diabetics.