A new study suggests that the Diabetes drug metformin, sold as Glucophage, may improve survival and clinical outcome in diabetic patients with heart failure, even though FDA labeling recommends against using the drug in these patients.

“Stable heart failure and Diabetes I think can be safely treated with metformin,” said Dr. Jeffrey A. Johnson of the University of Alberta in Edmonton.

Warnings against using metformin are based on past experience with phenformin - a similar drug that was taken off the market in the 1970s after being linked to hundreds of cases of lactic acidosis, a potentially life-threatening build-up of lactic acid in the blood that can damage vital organs.

However, there is a scarcity of information linking the newer drug metformin to this side effect, and recent studies suggest metformin may actually be more effective than so-called sulfonylurea drugs in reducing death from cardiac causes. According to Johnson, as many as 10 to 15 percent of diabetic patients with heart failure are prescribed metformin despite the labeling, largely due to the scarcity of other treatment options.

To investigate whether contraindications are warranted, the researchers identified 12,272 new users of oral antidiabetic drugs, 1833 of whom developed heart failure, and classified them based on the type of drug they were taking.

Compared to treatment with a sulfonylurea, treatment with metformin was associated with reduced hospitalization and death among patients with heart failure, the team reports in the October issue of Diabetes Care.

One third of patients on metformin died, compared with 52 percent of patients on sulfonylureas only. Seventy-seven percent of patients on metformin died or were hospitalized, compared with 85 percent of patients on sulfonylurea alone.

Given that this is a comparative study, Johnson notes, it’s not possible to say whether metformin improved outcomes or sulfonylureas worsened them. He points out that some older sulfonylureas have been shown to have some cardiotoxicity, while newer members of the drug family likely are safer.

Nevertheless, he adds, “we think there’s probably strong enough evidence to say that it should not be contraindicated. There’s no real evidence of the lactic acidosis happening in most patients with heart failure and Diabetes. We are speculating from our study that there may even be a benefit.”

SOURCE: Diabetes Care, October 2005.