Metformin in Heart Failure

We recently learned of an important change in the prescribing information for metformin, previously contraindicated in patients with type 2 diabetes accompanied by heart failure (HF) requiring pharmacological therapy. The contraindication was introduced to the label soon after the drug's U.S. release, when case reports emerged of HF patients taking metformin who developed lactic acidosis. It was never clear, however, whether either the HF or the medication were contributing factors. Subsequent analyses revealed a miniscule risk of lactic acidosis associated with metformin …