Metformin May Increase Heart Failure Risk in Men: Study

Side effects of the diabetes drug metformin may increase the risk of heart failure in men, according to the findings of a recent study.  

Researchers from the Washington University School of Medicine in St. Louis published a study in this month’s issue of the American Journal of Physiology — Heart and Circulatory Physiology, which suggests that men and women’s hearts handle metformin differently.

Metformin is a commonly drug used as a front-line treatment for type 2 diabetes. It is sold under several brand names, including Glucophage, Carbophage, Fortamet, Diabex and Riomet. It is also often used in combination with other diabetes drugs. Janumet is a combination of Januvia and metformin, while Actoplus Met is a combination of Actos and metformin, for example. The drug Avandamet, a combination of Avandia and metformin, was also used by some of the patients in this recent study.

Researchers in this latest study looked at 78 patients with type 2 diabetes before and three months after treatment involving metformin, Avandamet or a combination of metformin and a type of fish oil called Lovaza. According to their findings, metformin appeared to have different effects on the heart that were determined by gender.

The most dramatic difference was seen in metformin alone, researchers noted. While the drug was beneficial to the hearts of women, in men it caused their hearts to burn fat instead of sugar, which can lead to heart failure.

“We saw dramatic sex differences in how the heart responds to the different therapies,” Senior study author Robert J. Gropler, MD, said in a university press release. “Our study suggests that we need to better define which therapies are optimal for women with diabetes and which ones are optimal for men.”

Gender Differences May Affect Other Diabetes Drugs

The researchers suggest that the gender differences could resolve some contradicting scientific findings regarding diabetes drugs. They point out the ongoing controversy regarding the diabetes drug Avandia, which the FDA severely restricted, and several other countries removed from the market entirely, due to studies that suggested it increased the risk of heart attacks. Several weeks ago, the FDA reversed that decision, determining that the drug had no increased heart attack risk.

Researchers in this latest study suggest that the proportion of men and women in different Avandia studies may have led to different and conflicting results. They note that in their own study, when the men and women were looked at as a whole, no increased risk of heart disease was seen in the data.

Some reports suggest that as many as 100,000 heart attacks may have been caused by Avandia, and the drug’s manufacturer has reportedly paid more than $1 billion to settle Avandia heart attack lawsuits brought by former users of the medication who allege inadequate warnings were provided to consumers and the medical community.

The gender issue could affect other diabetes drugs as well, the researchers note.

Research has turned up conflicting data around a number of diabetes drugs. Some studies, for example, have suggested that Actos increases the risk of bladder cancer, while other reviews of the drug do not find those connections.

Actos (pioglitazone) is a type 2 diabetes drug that has been used by millions of Americans. However, it has been the subject of a growing number of product liability lawsuits over the past three years after concerns emerged about a connection between bladder cancer and Actos in September 2010.

In the federal court system, all Actos lawsuits are centralized before U.S. District Judge Rebecca H. Doherty in the Western District of Louisiana as part of an MDL or Multidistrict Litigation. A small group of cases in the federal Actos litigation are being prepared for early trial dates, which are expected to begin early next year.

Also, some studies have linked a class of drugs known as incretin mimetics, which includes Januvia and Byetta, to an increased risk of pancreatic cancer. However, when the FDA reviewed the data it could find no such link. That has not stopped the filing of dozens of pancreatic cancer lawsuits against the makers of the drugs.

In August, the U.S. Judicial Panel on Multidistrict Litigation (JPML) established centralized proceedings before U.S. District Court Judge Anthony J. Battaglia in the Southern District of California for all Byetta lawsuits, Januvia lawsuits, Janumet lawsuits and Victoza lawsuits filed in U.S. District Courts nationwide, which all involve individuals who allege they developed pancreatic cancer from side effects of the popular diabetes drugs.