Initiation of metformin rather than a sulfonylurea as treatment for type 2 diabetes among patients with chronic kidney disease (CKD) is associated with decreased mortality risk, a study found.

Patients with moderately to severely reduced estimated glomerular filtration rate (eGFR) experience the largest absolute risk reduction, according to researchers.

A team led by James S. Floyd, MD, of the University of Washington in Seattle, studied a cohort of 175,296 veterans who received care from the Veterans Health Administration for at least 1 year before initiating monotherapy for type 2 diabetes with either metformin or a sulfonylurea from 2004 to 2009. Of these patients, 5121 died. Compared with patients starting on a sulfonylurea, those starting on metformin had a 36% decreased risk of death, with the magnitude of risk reduction varying by eGFR, Dr Floyd and colleagues reported online ahead of print in the Journal of General Internal Medicine. Among patients with an eGFR of 90 mL/min/1.73 m2 or higher, those who started on metformin had a statistically significant 41% decreased risk of death compared with those who started on a sulfonylurea. Among patients with an eGFR of 45–59 mL/min1.73 m2, the metformin group had a statistically significant 20% decreased risk of death versus the sulfonylurea group.

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The investigators observed the greatest risk difference among patients with an eGFR of 30–44 mL/min/1.73 m2. In this group, patients started on metformin had 12.1 fewer deaths per 1000 person-years compared with those started on a sulfonylurea. Among patients with eGFR values of 90 mL/min/1.73 m2 or higher and 60–89 and 45–59 mL/min/1.73 m2, those started on metformin experienced 3.0, 4.3, and 3.4 fewer deaths per 1000 person-years, respectively, than those started on a sulfonylurea.

“These findings, together with results from previous studies, support the FDA’s guidance to consider metformin initiation among individuals with an eGFR of 45–59 mL/min/ 1.73m2, and suggests that metformin initiation may be beneficial among persons with even more severe CKD,” the authors concluded. “Given the number of glucose-lowering drugs available, further comparative effectiveness research is needed to guide prescribing practices, especially for high-risk patient populations.”

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Marcum ZA, Forsberg CW, Moore KP, et al. Mortality associated with metformin versus sulfonylurea initiation: A cohort study of veterans with diabetes and chronic kidney disease. J Gen Intern Med 2017; published online ahead of print.