NEW YORK (Reuters) - A leading doctor expressed concerns about the heart risks of GlaxoSmithKline Plc’s diabetes drug Avandia in a letter to the U.S. Food and Drug Administration seven years ago.

A scientist works in GlaxoSmithKline's plant in Singapore in a file photo. A leading doctor expressed concerns about the heart risks of GlaxoSmithKline Plc’s diabetes drug Avandia in a letter to the U.S. Food and Drug Administration seven years ago. REUTERS/Luis Enrique Ascui

John Buse, president-elect of the American Diabetes Association and faculty member at the University of North Carolina in Chapel Hill, cited “a worrisome trend in cardiovascular deaths and severe adverse events” among patients using the drug in a letter to the agency in March 2000.

The FDA sent Glaxo a warning letter in July 2001 after its own monitoring, saying the company’s sales representatives had played down safety concerns and asking the company to send out a letter to doctors warning them of the risks.

The company sent out the letters on September 6, 2001, according to an article in the New York Times, which first reported the story.

The news comes after a pooled analysis of dozens of trials, published in the New England Journal of Medicine on Monday, concluded that Avandia increased the risk of heart attack by 43 percent and cardiac-related death by 64 percent.

Glaxo has disagreed with the study findings. But shares in Europe’s biggest drugmaker have taken a hit since the article Monday, on fears for sales, profits and the risk of lawsuits that could potentially reach billions of dollars.

Avandia is Glaxo’s second-biggest seller, bringing in 1.6 billion pounds ($3.16 billion) and accounting for 7 percent of group revenues -- and significantly more of profits -- in 2006.

Glaxo, Buse and the FDA could not be reached immediately.

The Times cited Buse as saying that his opinion of Avandia had not changed, but that regulators should not rush to judgment and instead wait for the results of a larger study now being conducted by Glaxo.

The paper also cited a Glaxo spokeswoman as saying the company “strongly disagreed” with the allegations in Buse’s letter, “which we found to be unbalanced and unsubstantiated.”

“We took the time to meet and talk with Dr. Buse at length about his concerns,” the paper quoted spokeswoman Mary Anne Rhyne as saying. “We explained our reasons for why we disagreed with his characterization of the cardiovascular safety profile of Avandia.”

Referring to the FDA’s warning letter, the paper cited Rhyne as saying, “Action was taken at the time to ensure representatives of the company were accurately reflecting the label for the product in any commercial activity.”