New review confirms safety of metformin in patients with heart failure

Metformin-based strategies for glycemic control are safer than other antihyperglycemic strategies in patients with diabetes and heart failure, according to an update of a systematic review.
     The review of 8 observational studies that specifically evaluated metformin on mortality in patients with heart failure and diabetes found lower rates of all-cause mortality, all-cause hospitalizations, and heart failure-related hospitalizations in metformin recipients compared with controls, which consisted mostly of patients receiving sulfonylureas, said Dean T. Eurich, PhD, the study’s primary author.
     “The cumulative evidence would suggest that metformin is indeed safe in patients with heart failure and diabetes,” said  Eurich, Assistant Professor, Department of Public Health Sciences, School of Public Health at the University of Alberta, Edmonton, Alberta, Canada, who said the safety of metformin is further supported by “the fact that no study found an increase in adverse events with metformin.”
     The update included 8 cohort studies, 5 of which were published in 2008 (1 year after a previous systematic review was published by the same authors). No randomized controlled trials were identified, but all of the studies were of moderate methodologic quality.
     Metformin was associated with reduced mortality compared with controls in all 8 studies; achieving statistical significance in 6 studies. The overall pooled adjusted effect was a 22% reduction in all-cause mortality with metformin use versus comparators.
     Two of the 8 studies assessed all-cause hospitalization, and in these studies, metformin was associated with a 7% reduction in this endpoint compared with other therapies.
     In the 2 studies that report heart failure-related hospitalizations, metformin was associated an 8% reduction in this endpoint.
     The totality of available evidence indicates that metformin is safer and more effective than other treatments in patients with diabetes and heart failure, although it remains unclear “if the observed differences between antihyperglycemic drugs are due to a beneficial effect of metformin or whether the comparator agents are harmful; although the cumulative evidence suggests the former,” said Eurich.