Efficacy of metformin in the treatment of NIDDM - Meta-analysis

OBJECTIVE - The results differ concerning randomized controlled trials of the effects of metformin on blood glucose regulation and body weight. To get a systematic overview a metaanalysis of the efficacy of metformin was performed by comparing metformin with placebo and sulfonylurea. RESEARCH DESIGN AND METHODS - All randomized controlled trials published since 1957 were selected by searching the Current List of Medical Literature, Cumulated Index Medicus, Medline, and Embase. Meta-analysis was performed calculating weighted mean difference (WMD) of fasting blood glucose, glycosylated hemoglobin, and body weight. RESULTS - Nine randomized controlled trials comparing metformin with placebo and ten comparing metformin with sulfonylurea were identified. The WMD between metformin and placebo after treatment for fasting blood glucose was -2..0 mmol/l (95% CI -2.4 to -1.7) and for glycosylated hemoglobin -0.9% (95% CI -1.1 to -0.7). Body weight WMD was not significant after treatment. Sulfonylurea and metformin lowered blood glucose and glycosylated hemoglobin equally while there was a significant WMD of body weight (-2.9 kg [95% CI -4.4 to -1.1]) because of a 1.7-kg mean increase after sulfonylurea and a 1.2-kg mean decrease after metformin. CONCLUSIONS - Metformin lowers blood glucose and glycosylated hemoglobin significantly, compared with placebo. Metformin and sulfonylurea have an equal effect on fasting blood glucose and glycosylated hemoglobin, but the body weight is significantly lower after metformin compared with sulfonylurea treatment because of an increase in body weight after sulfonylurea treatment.