Meta-Analysis of Sulfonylurea Therapy on Long-Term Risk of Mortality and Cardiovascular Events Compared to Other Oral Glucose-Lowering Treatments

W. Ryan Powell, Cindy L. Christiansen, Donald R. Miller

Among the most pressing clinical decisions in type 2 diabetes treatments are which drugs should be used after metformin is no longer sufficient, and whether sulfonylureas (SUs) should remain as a suitable second-line treatment. In this article we summarize current evidence on the long-term safety risks associated with SU therapy relative to other oral glucose-lowering therapies. The MEDLINE database and Clinicaltrials.gov were searched for observational and experimental studies comparing the safety of SUs to that of other diabetes medications in people with type 2 diabetes mellitus through December 15, 2015. Studies with at least 1 year of follow-up, which explicitly examined major cardiovascular events or death in patients who showed no evidence of serious conditions at baseline, were selected for inclusion in meta-analyses. SU treatment was associated with an elevated risk relative to treatment with metformin (METF), thiazolidinedione (TZD), dipeptidyl peptidase-4 inhibitor (DPP-4), and glucagon-like peptide-1 (GLP-1) agonist classes, either when compared alone (as a monotherapy) or when used in combination with METF. Significant findings were almost entirely derived from nontrial data and not confirmed by smaller, efficacy designed randomized controlled trials whose effects were in the same direction but much more imprecise. Although much of the evidence is derived and will continue to come from observational studies, the methodological rigor of such studies is questionable. A key challenge for evaluators is the extent to which they should incorporate evidence from study designs that are quasi-experimental.