Metformin appears safe for heart failure patients, analysis finds

Metformin appears to be a safe option for glycemic control in heart failure patients, according to a recent meta-analysis.

The analysis included nine observational studies of the association between metformin and morbidity and mortality in patients with diabetes and heart failure, the majority of which were published in 2010. According to the analysis, patients on metformin had about 20% lower mortality than controls, who were most commonly taking sulfonylurea drugs: 23% versus 37% (P<0.001). A small but not statistically significant reduction in all-cause hospitalizations was also found in the metformin patients compared to controls.

The researchers also looked at the subgroups of patients who had reduced left ventricular ejection fraction (LVEF) or chronic kidney disease, and in both cases, metformin was associated with slightly reduced mortality (pooled adjusted risk estimates, 0.91 and 0.81, respectively). No increased risk of lactic acidosis was found in metformin patients. The results were published online by Circulation Heart Failure on March 18.

Despite historical concerns about its use in heart failure patients, metformin appears to be at least as safe as other glucose-lowering treatments for these patients (including the high-risk groups with reduced LVEF and kidney disease) and should be the treatment of choice, the study authors concluded. This finding supports both current guidelines from medical specialty societies and recent decisions by the FDA and Canadian regulators to remove a black-box contraindication concerning use of metformin in heart failure patients.

The authors did acknowledge a risk of confounding because the evidence is based entirely on observational trials, but they said that randomized trials in this patient population are rare and not likely to be expanded. However, a number of studies in animal models of heart failure have suggested potential benefits of metformin, the authors noted.