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Metformin vs Sulfonylurea for Type 2 DM With Impaired Kidney Function

Information sourced from NEJM Journal Watch:

Monotherapy with Metformin vs. Sulfonylureas for Type 2 Diabetes with Impaired Kidney Function

In an observational study, metformin was associated with fewer deaths at 5 years.

In 1995, the FDA approved metformin for patients with type 2 diabetes; however, the label advised clinicians to avoid prescribing metformin to patients with impaired kidney function because of concerns about lactic acidosis. But in 2016, the FDA endorsed metformin’s safety in patients with mild-to-moderate kidney function impairment. To determine whether risk for death differs following initiation of metformin monotherapy or sulfonylurea monotherapy among veterans with type 2 diabetes and chronic kidney disease, researchers conducted this cohort study of 175,000 patients who initiated these drugs as monotherapy at Veterans Affairs hospitals between 2004 and 2009.

About 5000 deaths occurred during follow-up. Adjusted for multiple potential confounders, metformin monotherapy (compared with sulfonylurea monotherapy) was associated with a significant 36% lower relative risk for death. Within estimated glomerular filtration rates of ≥90, 60–89, 45–59 and 30–44 mL/minute/1.73 m2, metformin monotherapy was associated with 3.0, 4.3, 3.4, and 12.1 fewer deaths per 1000 person-years, respectively; all differences were significant.


Although residual confounding is possible, this study shows that initiation of metformin monotherapy versus sulfonylurea monotherapy among patients with type 2 diabetes and mild-to-moderate kidney function impairment is associated with lower risk for death. This study should be reassuring to clinicians and to diabetic patients with impaired kidney function. Metformin should be prescribed preferentially over sulfonylureas in this group of patients.

Paul S. Mueller, MD, MPH, FACP reviewing Marcum ZA et al. J Gen Intern Med 2018 Feb.


Marcum ZA et al. Mortality associated with metformin versus sulfonylurea initiation: A cohort study of veterans with diabetes and chronic kidney disease. J Gen Intern Med 2018 Feb; 33:155.

NEJM Journal Watch is produced by NEJM Group, a division of the Massachusetts Medical Society. Copyright ©2018 Massachusetts Medical Society. All rights reserved.

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