A commonly used diabetes drug increases the risk of stroke, heart disease, and death, according to a study released today in the Journal of the American Medical Association.

In a study of nearly a quarter million Type 2 diabetics on two diabetes drugs, the risk of heart failure was 25 percent greater on Avandia than the competitor drug, Actos, and the risk of stroke was 27 percent greater.

It's not the first time that Avandia has been in the news for having harmful side effects. A study in the New England Journal of Medicine suggested the same thing in 2007 and prompted an investigation by the Food and Drug Administration.

Because there are other drugs without such extreme side effects, doctors in the study are questioning why physicians would prescribe Avandia regularly to diabetics. The fact that it's still on the market is a classic example of the FDA's failure to protect patients, says the study's author.

"What we're reporting in this study today was available to the FDA in 2007," said David Graham, a doctor at the Center for Drug Evaluation and Research at the FDA in Maryland. But the agency waited three years for more definitive proof of harm, he said, even though roughly 10 studies have shown Avandia to be less safe than its alternative, he said.

"That keeps unsafe drugs on the market and patients are the ones who suffer," said Graham.

But other doctors are skeptical that the evidence against Avandia is definitive.

"I think the data is inconclusive," said Dr. Richard Bach, the director of the Cardiac Intensive Care Unit at the Washington University School of Medicine in St. Louis, who has led his own clinical trial testing the safety of the drug among diabetics. The FDA issued a safety alert in 2007 after an analysis of 42 studies suggested the drug put patients at risk for cardiovascular problems. Some suggested Avandia was harmful, while others did not.

"A physician should consider the weight of that evidence and the fact that it's been discrepant in various studies," said Bach, who said he hadn't seen the JAMA study yet. "I would not say that the totality of evidence weighs in to say that the drug always has harm."