[Role of metformin in diabetes treatment--is metformin falling from grace?]

Two recent meta-analyses focused on the risk-benefit ratio of metformin in the treatment of type 2 diabetes mellitus. Both studies conclude that the risk-benefit ratio of metformin monotherapy or combined with insulin is uncertain. In our opinion, the interpretation of the known literature in these meta-analyses could be flawed. To ascertain the effects of metformin on cardiovascular end-points, a follow-up period of at least 8 years proved necessary. However, these meta-analyses included a number of studies with a limited follow-up period, thus impairing the possibility to make a proper comparison of the long-term effects of metformin. In addition, one meta-analysis based the weight of included studies on the number of events in all studies, including two safety studies, as opposed to the number of studied patients.