The panel could recommend not changing the drug's label or putting a "black box" warning on the label; they could even suggest that the drug be pulled from the market. While the FDA isn't required to adopt an advisory panel's recommendation, it typically does.

The concerns about Avandia (rosiglitazone), part of a class of drugs for diabetes called thiazolidinediones, are based on a meta-analysis of published studies that suggested the drug increases the risk of heart attack by 43 percent. That finding was first published May 21 in the New England Journal of Medicine, in a paper co-authored by Dr. Steven Nissen, chairman of cardiovascular medicine at the Cleveland Clinic.

Nissen was one of the earliest critics of the arthritis drug Vioxx, which was withdrawn from the market in 2004 due to heart attack concerns, and he will be testifying at Monday's meeting.

Dr. Larry Deeb, president for medicine and science at the American Diabetes Association, believes that Avandia should continue to be available to diabetics because the increased risk of heart attack has not been proven conclusively.

"A decision do to something should not be based on a nebulous risk," Deeb said. "There probably should be a warning on the box, because there is enough concern."

Deeb believes the FDA should call for a study to thoroughly review any heart risks associated with the drug's use. "It's premature to withdraw the drug. I am anxious about pulling [a drug] that has done some good off the market based on a meta-analysis," he said.

Dr. Sidney Wolfe, director of Public Citizen's Health Research Group, who will also be giving testimony, has previously spoken out against Avandia. "We have warned readers of WorstPills.org since the end of 2004 that they should not use this drug," he said in a prepared statement in May.

"Despite prior knowledge of serious cardiac problems, the FDA has failed to require Glaxo [GlaxoSmithKline, the drug's maker] to adequately warn about the dangers of this drug that should be, at best, a last-choice treatment for type 2 diabetes," Wolfe said. "In addition to the accumulating evidence of its risks, it is not even as effective as other diabetes drugs in lowering blood sugar or hemoglobin A1C, a measure of glucose control."

For its part, GlaxoSmithKline insists the drug does not increase the risk of heart attack. "We don't believe that a warning about heart attack should be on the label," said Dr. Andy Zambanini, director of clinical development at GlaxoSmithKline.

"Avandia is one of the most studied medicines in the diabetes field," Zambanini said. "We have looked at all the available data both from short-term trials, long-term trials and real-world data, in terms of epidemiology. There is really no evidence of an increase in cardiovascular death with Avandia. And when you look at Avandia and compare it with all the other similar agents, there really is no difference in heart attack risk."

One of the studies that GlaxoSmithKline is relying on to make its case is the RECORD (Rosiglitazone Evaluated for Cardiac Outcomes and Regulation of Glycemia in Diabetes) trial. The study, sponsored by Glaxo, was specifically designed to determine the risks for heart attack from Avandia.

The FDA's Graham, associate director for science and medicine in the agency's Office of Surveillance and Epidemiology, disagrees with Glaxo's interpretation of the RECORD study. In a report submitted by the FDA to the advisory panel, Graham concluded:

"RECORD does not now, nor will it at completion, provide meaningful evidence to demonstrate with any degree of certainty that RSG [Avandia] does not increase the risk of acute myocardial infarction [heart attack] or sudden death, or the APTC outcome. The biased design of RECORD renders it useless as an objective measure of Avandia's cardiovascular safety. Its results cannot be trusted because they are too subject to bias. The design and statistical power limitations of RECORD are such that it is probably unethical to continue the study because it cannot produce scientifically reliable or valid results."

Zambanini countered by saying that the RECORD study has seen very few cardiac deaths. "To say that this study is of no value isn't true," he said.

More than 2 million people worldwide take Avandia for type 2 diabetes, the most common form of diabetes in which the body doesn't produce enough of the hormone insulin or cells ignore the insulin, leading to a buildup of blood sugar that can pose a range of health risks. The drug generates $3.2 billion in annual sales for GlaxoSmithKline.

Currently, there is a warning on Avandia's label that it increases the risk of another cardiovascular problem called congestive heart failure. This is a chronic condition caused by the heart's failure to pump normally, allowing fluid to build up in the body. Heart failure causes difficulty breathing and also affects the kidneys' ability to dispose of sodium and water.

In May, the FDA said it wanted a stronger warning about the risk of heart failure on Avandia's label. Glaxo is "still in negotiation with the FDA about a new warning label on heart failure and we expect to release that information soon," Zambanini said.

Critics of the drug contend there are alternatives to Avandia that don't have the same risk for heart failure or heart attack They include metformin, Actos, Amaryl, Glyburide and others.

More information

Learn more about diabetes drugs from the U.S. Food and Drug Administration.