This time it’s specifically in reference to heart failure, which is listed as a contraindication in the product labeling. As I recently blogged, the vast post marketing experience with metformin indicates that it is safe, and that lactic acidosis has been difficult to attribute to it despite widespread contraindicated prescribing.
This large observational study from Diabetes Care showed that heart failure patients treated with metformin, as monotherapy or in combination with sulfonylureas, had significantly lower rates of mortality and hospitalization than those treated with sulfonylurea monotherapy. The average follow up period was 2.5 years. The mechanism may be the alleviation of hyperinsulinemia.
The authors suggest that the strict labeling of metformin may represent unfounded concerns which have deprived patients of beneficial treatment, and challenge the precautionary principle with this statement: Although "patient safety" studies often seem to focus on finding and reducing the use of previously widely prescribed medications that are of unproven benefit or even harmful, our study should serve as a reminder that there is another side to the patient safety coin—some medications that are currently considered contraindicated may have been defined as such on the basis of little or no evidence beyond pathophysiological rationale. Since this rationale alone is considered insufficient evidence for efficacy, it should also be insufficient to declare harm. We believe that the onus in the patient safety literature should shift to acknowledge that both types of patient safety issues can lead to suboptimal prescribing practices.