To the Editor: The clinical review by Dr Phung and colleagues1 showed that the different classes of noninsulin antidiabetic drugs added to metformin therapy in type 2 diabetes provided similar reduction in hemoglobin A1c (HbA1c) compared with placebo. This seems to point to the equivalence of these drugs on glycemic control when optimal metformin therapy fails. However, the evidence supporting the authors' statement that “[t]he rate of HbA1c goal attainment [<7%] was also similar among classes of drugs” is at best scanty. More than half of the trials (14 of 27) did not report the HbA1c goal achieved; moreover, in those trials doing so, the evidence is based on the results of 1 trial only for sulfonylureas, glinides, thiazolidinediones, and glucagon-like peptide-1 (GLP-1) analogs (Table 2 in the article).
Giugliano D, Esposito K. Adding Noninsulin Antidiabetic Drugs to Metformin Therapy for Type 2 Diabetes. JAMA. 2010;304(4):405-407. doi:10.1001/jama.2010.1020