Cette metformine, si connue. Si méconnue pour ses taux thérapeutiques…

To establish whether or not there is a literature consensus on the “therapeutic concentrations” of metformin, we systematically searched the scientific literature with the key-words “metformin” and “therapeutic concentration”. When the suggested values were defined by citing a literature reference, the types of studies in cited references and the concordance of data between the citations and theirs sources were studied. We identified 120 documents, which reported or cited 65 different “therapeutic” plasma metformin concentrations or ranges. The values ranged from 0.129 to 90 mg/L, and the lowest and highest boundaries were 0 and 1800 mg/L. Only four original research studies determined a “therapeutic concentration”. Fifty-four publications cited previous studies as defining the therapeutic concentrations, whereas 62 publications did not even cite a supporting reference. The supporting references were mostly reviews, pharmacokinetic studies and in vitro studies. In the 54 publications that cited references, concordance between the wording of the citation and the true nature of the source data was observed in only 23 cases (42.6%). In conclusion, although metformin is the key medication in first-line treatment of type 2 diabetes, major methodological and/or conceptual errors have confounded the literature on its therapeutic concentrations.