Study shows metformin is safe for patients with mild-to- moderate kidney disease

Over the years, there has been uncertainty over which drugs are best for patients with Type 2 diabetes and one of its common complications, kidney disease. An observational study using medical record information from nearly 50,000 U.S. military veterans sheds new light on this issue.

Among the 30 million U.S. adults with Type 2 diabetes, 20% have impaired kidney function. In patients like this, metformin, the recommended first-line drug therapy for Type 2 diabetes, is associated in the new study with 20 percent decreased risk of major adverse cardiovascular events when compared to a class of common diabetes drugs called sulfonylureas.

The lower risk associated with metformin translates as 5.8 fewer of these events per 1,000 person-years compared to sulfonylureas. The events tracked in the study include heart attack, stroke, transient ischemic attack and cardiovascular death.

The study by researchers at Vanderbilt University Medical Center appears in JAMA, the flagship journal of the American Medical Association.

Until recently the use of metformin in patients with diabetes and impaired kidney function was cautioned against due to safety concerns. The effectiveness of metformin demonstrated in this study will further support a potential change in prescribing practices for these patients. We believe these results should encourage providers to continue use of metformin in mild-to- moderate kidney disease,"

Christianne Roumie, MD, MPH, study lead and associate professor, Medicine and Pediatrics, VUMC

Among patients receiving care from 2001 through 2016 within the national Veterans Health Administration, 174,882 were newly diagnosed with Type 2 diabetes, started using either metformin or a sulfonylurea, and developed impaired kidney function.

The new study is focused on 24,679 patients who continued on metformin and 24,799 who continued on a sulfonylurea (the study excluded patients who added other diabetes medications on top of these drugs). To account for other factors that might influence cardiovascular risk, Roumie and colleagues evaluated patient characteristics like age, sex, race, other illnesses, body mass index and blood pressure.

Median follow-up was 1.0 years for patients taking metformin, 1.2 years for sulfonylurea users. Metformin users experienced 1,048 adverse events while sulfonylurea users experienced 1,394, or 23.0 and 29.2 per 1,000 person-years, respectively. After adjustment for other risk variables, this amounted to a 20% reduced risk with metformin compared to a sulfonylurea.