Vote in Favor of Insulin

Abstract

Hartmann et al postulate that metformin should be substituted by sitagliptin in patients with an eGFR below 60 mL/min. This recommendation is surprising—on the one hand, compensated renal failure is increasingly being challenged as a contraindication to metformin (1). In the United Kingdom, only a creatinine concentration of >1.5 mg/dL is regarded as a contraindication. A recently published Cochrane review (2) did not find any indication that use of metformin leads to lactic acidosis more often than other antidiabetes drugs. On the other hand the recommendation is surprising because sitagliptin is a substance about which no more is known than the fact that it lowers blood glucose concentrations. In the meantime, many reports have been received about the potential of sitagliptin to cause harm (3). A short monograph from the Drug Commission of the German Medical Association does not recommend its use in moderate or severe renal failure because not enough studies exist. The UKPDS 34 showed that near-identical lowering of HbA1c benefits patients to extremely varying degrees, depending on whether metformin or other substances are used. Just now, the European Medicines Agency has ordered to take rosiglitazone off the market—another sign for the fact that lowering HbA1c by means of medication is a very weak indicator of its use. It is not clear why the article recommends sitagliptin, a substance about which we do not know whether its use affects patient-relevant end points positively or negatively. Why did the authors not vote in favor of insulin, just in case that metformin should really not be used in more severely restricted renal function?