Studies Suggest Heart Risk With Diabetes Drug Avandia

June 28, 2010 -- People who take the widely used diabetes drug Avandia may be putting themselves at higher risk of developing fatal heart problems, according to two large studies published today in the Journal of the American Medical Association.

The first study analyzed 56 studies totalling more than 35,000 patients that compared Avandia to other drugs used to lower blood sugar in patients with diabetes. Patients taking Avandia were 33 percent more likely to have a heart attack compared to those on other treatments, according to the study.

The second study, by Dr. David Graham, associate director of the Food and Drug Administration, analyzed data collected from more than 220,000 elderly patients in a Medicare health insurance program who either took Avandia or its equivalent class drug Actos. While the study found an increased risk of heart failure, stroke and death among patients taking Avandia compared to those taking Actos, there was no difference in risk of heart attack among those taking Avandia and Actos.

"There is no reason for this drug to be given to patients," said Dr. Steven Nissen, chairman of cardiovascular medicine at the Cleveland Clinic, and author of the first study.

Watch ABC News' senior health and medical editor Dr. Richard Besser's report on Avandia tonight at 6:30 p.m. ET on "World News With Diane Sawyer"

These studies are not the first to question Avandia's safety. GlaxoSmithKline first reported the results of its review -- which found an increased risk of heart attacks in Avandia patients -- to the FDA in 2005, but neither the company nor the federal agency issued a public warning at the time.

A 2007 study conducted by Nissen first raised public concern about Avandia's cardiovascular effects. The FDA decided in November 2007 to leave the drug on the market, with the addition of a black box warning of the risk of heart attack.

Since then, the popular diabetes drug lost more than half of its sales, although it still generated more than $1 billion in revenue last year alone.

Nissen said his latest study, the largest to date analyzing the potential adverse effects of Avandia, confirmed his previous findings. Still, dueling reports have gone back and forth on whether the cardiovascular risk associated with Avandia is real.