[Medication of the month. Sitagliptin-metformin fixed combination (Janumet)]

Type 2 diabetes is a complex disease with the coexistence of several pathophysiological abnormalities such as a defect of insulin secretion, a relative hyperglucagonaemia, an increased hepatic glucose production and a muscular insulin resistance. In order to tackle all these abnormalities, the coadministration of several drugs with complementary actions is frequently required. Janumet is a fixed-dose combination of sitagliptin, a specific inhibitor of dipeptidylpeptidase-4 that blocks the rapid degradation of so-called incretin hormones (resulting in a potentiation of insulin secretion and reduction of glucagon secretion in a glucose-dependent manner), and of metformin, a biguanide compound that reduces glucose hepatic production and slightly improves insulin sensitivity. This pharmacological combination improves glucose control without inducing hypoglycaemia or weight gain. The tolerance profile is rather good, with (digestive) side effects and contraindications (risk of lactic acidosis in case of renal insufficiency) attributable to metformin. Janumet (50/850 mg or 50/1.000 mg), twice daily, is indicated in the treatment of type 2 diabetes and is currently reimbursed in Belgium after failure of metformin monotherapy or the prior demonstration of the efficacy of adding sitaglitptin (Januvia) to metformin.