Safety of add-on sulfonylurea therapy in patients with type 2 diabetes using metformin: a population-based real-world study

INTRODUCTION: Metformin is the initial oral antihyperglycemic agent (OHA) of choice for most patients with type 2 diabetes (T2D). However, more than one agent is often required for optimal glucose control. As the choice of preferred second OHAs is less well defined, we sought to compare the real-world safety of sulfonylureas to other OHAs as add-on therapy to metformin in patients with T2D. RESEARCH DESIGN AND METHODS: This retrospective cohort study included adults in Manitoba, Canada with T2D from 2006 to 2017. Using a new-user design, we divided patients who started on metformin into two groups: add-on therapy with a sulfonylurea and add-on therapy with a different OHA. Outcomes included all-cause mortality, cardiovascular events, and major hypoglycemic episodes. We calculated propensity scores and applied inverse probability of treatment weights to each individual. We compared groups using Cox proportional hazards regression and explored differences in HRs between pre-2008 (acarbose, meglitinides, and thiazolidinediones) and post-2008 (dipeptidyl peptidase-4 inhibitors, glucagon-like peptide-1 receptor agonists, and sodium-glucose linked transporter-2 inhibitors) OHAs. RESULTS: Our cohort included 32 576 individuals (28 077 metformin plus sulfonylurea and 4499 metformin plus ‘other’). Patients newly prescribed a sulfonylurea in the setting of metformin had a higher risk of all-cause mortality (HR 1.44, 95% CI 1.12 to 1.84, p=0.005) and major hypoglycemic episodes (HR 2.78, 95% CI 1.66 to 4.66, p<0.001) than those prescribed an ‘other’ OHA. No differences in cardiovascular events were observed (HR 0.99, 95% CI 0.81 to 1.22, p=0.92). In subgroup analyses, mortality and cardiovascular event risk was higher in patients prescribed sulfonylureas versus post-2008 OHAs. CONCLUSIONS: Sulfonylureas as add-on therapy to metformin are associated with increased risk of all-cause mortality and major hypoglycemic episodes compared with ‘other’ OHAs. Post hoc analysis suggests newer OHAs may be preferred to sulfonylureas as second-line therapy for glycemic control.