WEDNESDAY, Nov. 14 (HealthDay News) -- The popular diabetes drug Avandia -- which has been linked to the risk of heart failure and, more recently, heart attack -- will carry a revised "black box" warning noting the heart attack risk, even though the research on heart attack is inconclusive, U.S. officials said Wednesday.

GlaxoSmithKline, the maker of Avandia (rosiglitazone), a drug used to treat type 2 diabetes, has agreed to add the new warning to the existing black box warning on the drug's label, according to U.S. Food and Drug Administration officials.

"We are announcing an update to the existing box warning on Avandia," Dr. Janet Woodcock, acting director of the FDA's Center for Drug Evaluation and Research, said during a midday teleconference. "A black box is the strongest form of warning, and we are adding another warning to that black box."

Despite the revised warning label, the FDA said it isn't seeking to have the drug withdrawn from the market, because the evidence for the increased heart-attack risk is not conclusive.

"We are keeping Avandia on the market, because we have concluded there isn't enough evidence to indicate that the risk of heart attack is higher for Avandia than other type 2 diabetes treatments," Woodcock said.

Woodcock said the FDA has asked GlaxoSmithKline to conduct a long-term study comparing Avandia with other type 2 diabetes drugs. The trial will most likely start in a year, and full results won't be available until 2014.

The new labeling follows recommendations made by the FDA's Endocrine and Metabolic Advisory Committee and Drug Safety and Risk Management Advisory Committee. In July, the committees recommended keeping Avandia on the market, pending a review of additional data. The committees also said the drug's label should carry a warning of the potential for increased risk of heart attacks.

Controversy over Avandia started in May, when a study published in the New England Journal of Medicine, found a 43 percent increased risk of heart attack among patients taking the drug. The study was carried out by Dr. Steven E. Nissen, chairman of the Cleveland Clinic's department of cardiovascular medicine, and his colleague Kathy Wolski. Nissen said he uncovered the risk after poring over data from 42 studies of Avandia.

Both the FDA and GlaxoSmithKline continue to say that the evidence for the risk of heart attack with Avandia is inconclusive.

"Avandia remains a safe and effective medicine for most patients with type 2 diabetes when used appropriately," Dr. Ronald Krall, GlaxoSmithKline's chief medical officer, said in a prepared statement. "Given the severity of this disease and the importance of Avandia in helping patients manage their diabetes, we will continue to work with the FDA to conduct more studies about the safety and benefits of our medicine."

The new warning states: "A meta-analysis of 42 clinical studies (mean duration 6 months; 14,237 total patients), most of which compared Avandia to placebo, showed Avandia to be associated with an increased risk of myocardial ischemic events such as angina or myocardial infarction. Three other studies (mean duration 41 months; 14,067 patients), comparing Avandia to some other approved oral antidiabetic agents or placebo, have not confirmed or excluded this risk. In their entirety, the available data on the risk of myocardial ischemia are inconclusive."

The FDA is advising people with type 2 diabetes who have heart disease or are at risk of a heart attack to discuss their use of Avandia with their doctor to evaluate treatment options. The agency is also advising doctors to monitor patients who have cardiac risk and are taking the drug.

In August, Avandia's warning label was changed, to state that the drug and others in its class may worsen heart failure -- a condition in which the heart does not adequately pump blood -- in some patients. The association between Avandia and increased risk for heart failure has been known since 1999, when the drug was first approved.

Woodcock noted that Avandia and the other oral anti-diabetes drugs, called thiazolidinediones, have not been shown to prevent cardiovascular risk as a byproduct of reducing blood sugar.

In light of this, the FDA is asking all manufacturers of approved oral anti-diabetes drugs to include a statement on their label saying that there is no data that the drugs have the ability to protect the heart.

More information

For more on diabetes drugs, visit the U.S. Food and Drug Administration.

SOURCES: Nov. 14, 2007, teleconference with Janet Woodcock, M.D., acting director, Center for Drug Evaluation and Research, U.S. Food and Drug Administration; Nov. 14, 2007, news release, GlaxoSmithKline, Philadelphia

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