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Medical Rounds

Kidney Disease: Allaying Concerns over Metformin

Metformin is the first-line medication for treatment of type 2 diabetes in adults and the fifth most commonly used drug in the United States. However, there has been a long-standing concern in the medical community about prescribing metformin for people with both diabetes and chronic kidney disease (CKD). The worry has been that metformin may cause a life-threatening condition called lactic acidosis.

Now results of a large-scale Johns Hopkins study suggest that metformin is safe for most people with diabetes who also have CKD. The study of more than 150,000 adults found that metformin’s association with the development of lactic acidosis was seen only among patients with severely decreased kidney function. The investigators reported their findings in JAMA Internal Medicine.

The Food and Drug Administration recently revised its labeling of metformin so the drug could be used more by CKD patients, and some regulatory and professional society guidelines cautiously support use of the drug by patients with diabetes and moderate kidney disease. But data addressing the drug’s safety for patients with moderate to severe kidney disease had been inconclusive, says study senior author Morgan Grams.

A better assessment of acidosis risk could “provide reassurance that millions of people with diabetes and CKD may be able to safely use metformin,” Grams says. Past studies show that metformin has multiple benefits beyond controlling blood sugar, including less weight gain, a lower risk of heart attack and even higher long-term survival than other medications that patients take to control blood sugar.

About 380 million people worldwide and 29 million people in the United States are affected by diabetes. Approximately 19 percent—or around 5 million—of those in the U.S. with diabetes also have CKD, Grams says.

“Our study demonstrates that the first-line and common diabetes medication is safer in patients with CKD than once thought,” Grams says. “From a public health perspective, the potential benefits of using metformin for patients with diabetes and CKD are vast, given the increasing number of people affected with both diseases worldwide.”

Metformin, beyond having potential health benefits, is relatively inexpensive. The medication can be obtained for $4 per month for the 500-milligram dose. In contrast, some of the newer diabetes agents can cost more than $400 per month.