The Associated Press

WASHINGTON — Hearings begin today on whether the drug Avandia should stay on the market.

Ahead of the hearings, FDA scientists have blasted a study by drug maker GlaxoSmithKline (NYSE: GSK) used to defend the safety of the once high-riding diabetes drug, which fell out of favor because of potential ties to heart attacks.

In fact, one FDA reviewer says the study actually makes the case against leaving Avandia on the market.

(Information about the FDA meeting and background documentation is )

For the Food and Drug Administration, Avandia represents the latest in a series of drugs that were approved years ago, only to be called into question later because of safety concerns.

Regulators have three likely options: Add more warning labels; limit which doctors can prescribe Avandia; or, pull it from the market altogether.

The FDA reviewed dozens of studies of Avandia, including one Glaxo has pointed to as proof of the drug’s safety. But an FDA reviewer said the study was plagued by "serious flaws" and actually supports the case against Avandia.

The drug works by increasing the body’s sensitivity to insulin, a key protein needed for digestion that diabetics don’t adequately produce.

People with diabetes are unable to properly break down carbohydrates, either because their bodies do not produce enough insulin or because of resistance to insulin. They are at higher risk for heart attacks, kidney problems, blindness and other serious complications.

Avandia was GSK’s third best-selling drug in 2006 with U.S. revenue of $2.2 billion, according to health care statistics firm IMS Health. But safety concerns swirling around the drug have pummeled sales over the last three years, with sales falling 75 percent to $520 million last year.

In 2007 an analysis of dozens of studies first linked the drug to heart attacks. The FDA responded by adding a warning label to the drug later that year.

GSK, which maintains its U.S. headquarters in Research Triangle Park, N.C., has argued for years that Avandia’s safety should be assessed only based on clinical trials, considered the gold standard of medical research.

But the FDA reviewer said GSK’s chief trial "was inadequately designed and conducted to provide any reassurance" about the heart safety of Avandia.

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