Metformin May Be Underutilized In Patients With Modest Kidney Disease

MedicalResearch.com Interview with:
James Flory MD, MSCE
Division of Endocrinology and Department of Healthcare Policy and Research
Weill Cornell Medical College, NY NY

Medical Research: What is the background for this study? What are the main findings?

Dr. Flory: Metformin is the first-line drug for type 2 diabetes, with much better evidence for safety and improved clinical outcomes than any alternative. The one major safety concern about metformin is the fear that it can cause lactic acidosis, which led to a Food and Drug Administration black box warning against using metformin in patients with even a modest degree of renal impairment. These fears and warnings were based on serious problems with an older drug in the same class, not on experiences with metformin itself, and over the past 20 years it has become clear that the risk of lactic acidosis with metformin is extremely low, and that this warning against the use of the drug in mild renal failure is overly strict. (Dr. Lipska and colleagues published a superb review of this issue a few years back: Diabetes Care June 2011 vol. 34 no. 6 1431-1437)

This is important from a public health perspective because so many patients with diabetes have mild to moderate kidney disease, and we were concerned that the FDA warning was preventing the use of metformin in these patients. Our study was intended to estimate how many patients who would benefit from metformin are not taking it because they have mild kidney disease.

We found that rates of metformin use are much lower in patients with mild kidney disease – just the population where the FDA warning discourages use, but modern data show that metformin is safe. In all, at least 1 million patients with type 2 diabetes who would benefit from metformin appear not to be taking it because clinicians are following the FDA warning and being too conservative.

Medical Research: What should clinicians and patients take away from your report?

Dr. Flory: Clinicians and patients should be aware that in mild to moderate renal failure (30 to 60 ml/min glomerular filtration rate), metformin is still safe and is an excellent option for treating type 2 diabetes.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Flory: We think the evidence assembled by other researchers already makes a very strong case that metformin is safe in mild to moderate renal failure, and that while policy changes are needed, additional research on that specific question is not a high priority. However, we are overdue for more randomized clinical trials assessing the health benefits of metformin in special populations, including patients with diabetes and more advanced kidney disease where it is not as clear that metformin is safe.

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