Benfluorex under trade name Mediator was launched in 1976 for controlling blood sugar levels in people with type 2 diabetes. In 2009 this drug together with others medicines containing it was withdrawn because of the risk of heart valve disease. The mechanisms by which benfluorex reduces hepatic gluconeogenesis are markedly different from those of metformin, the main antidiabetic compound used in the world. It was suggested that inhibition of gluconeogenesis by benfluorex was, at least in part, due to a decrease in mitochondrial β-oxidation. First, benfluorex decreased acetyl-CoA concentration, which in turn would reduce pyruvate carboxylase activity and release its inhibitory effect on pyruvate dehydrogenase. Second, benfluorex decreased both the ATP-to-ADP and the NAD+-to-NADH ratios, leading to a reduced gluconeogenic flux at the level of 3-phosphoglycerate kinase and GAPDH. Changes in cellular redox state represent probably the main mechanism by which benfluorex reduces glucose production in hepatocytes.