The maker of the controversial diabetes pill Avandia pointed to early results of its own study Tuesday, saying they offered reassuring evidence the drug doesn't raise heart risks. However, outside experts called the results inconclusive at best and a sign of greater risk at worst.

The study compares Avandia with two other diabetes pills in nearly 4,500 people around the world. Drug maker GlaxoSmithKline PLC released results of the first few years of a six-year study showing similar rates of heart-related deaths and hospitalizations among those on Avandia versus those on the other drugs.

But some doctors said the results showed slightly more heart problems with Avandia — a bad sign even though the difference was so small that it could have occurred by chance alone. They also contend there are problems with the way the study was done.

"This study, which was designed to show the benefit of rosiglitazone (Avandia), if anything shows the opposite," said Dr. David Nathan, chief of diabetes care at Massachusetts General Hospital.

Nathan, who has no role in the study and has received speaker fees from Glaxo and other drug companies, wrote an editorial accompanying it, which was published online by the New England Journal of Medicine. The journal rushed it out because a congressional panel will hold a hearing Wednesday on the drug's risks and the response by the federal Food and Drug Administration, which has been criticized for being too lax about safety concerns.

The problem came to light two weeks ago, when the journal published pooled results of 42 studies suggesting that Avandia raised the risk of heart attacks by 43 percent and possibly heart-related deaths.

British-based GlaxoSmithKline insists that the drug is safe and effective. Company officials say their own analysis found a similar greater risk of heart attack, but that better information, like the results announced on Tuesday, do not back that up.

"Overall, we feel these results are very reassuring," Dr. Murray Stewart, Glaxo's vice president of clinical development, said during a telephone news conference.

More than 6 million people worldwide have taken Avandia or a related drug, Avandamet, since it came on the market eight years ago. About 1 million Americans use it now.

It is used to treat Type 2 diabetes, the most common form of the disease, which is linked to obesity and afflicts 18 million Americans and 200 million people worldwide. The disease occurs when the body does not make enough insulin or cannot effectively use what it manages to produce.

Avandia's label already warns about possible heart failure and other heart problems when taken with insulin. The drug also raises LDL, or bad cholesterol, and can cause fluid retention and weight gain.

But the possibility that it also raises heart attack risk caused alarm because two-thirds of diabetics die of heart problems and are especially vulnerable to drugs that increase that danger.

The new study, called Record, was paid for by Glaxo, led by doctors at Newcastle University in England, and done at 327 medical centers in Europe and Australia.

Half of patients were given Avandia on top of diabetes drugs, metformin or sulphonylurea; the others received the other two drugs and not Avandia. The partial results cover almost four years of the study.

In all, 217 people taking Avandia had a heart-related death or hospitalization versus 202 of the others. Some doctors said this measure could underestimate the risk of the drug and that a better test would have measured all heart attacks or heart-related deaths.

As it stands now, no firm conclusions can be drawn from these results because so few of these problems occurred in either group, said Dr. Alvin C. Powers, director of the Vanderbilt University diabetes center. He has no financial ties to any diabetes drug makers or this study.

"It doesn't make it safe, it doesn't make it dangerous. It's not a conclusive answer," he said.

But the trend "is going in the wrong direction" for Avandia, said Dr. Steven Nissen of the Cleveland Clinic, whose original study brought the problem to light.

The new Glaxo study has several drawbacks, experts said. One is that it was "open label," meaning that doctors and patients knew what drugs were being prescribed. That can affect reporting side effects and results.

It also can mean that the patients getting one drug were different from those prescribed another. For example, those given Avandia, which raises "bad cholesterol," may also be more likely to be on cholesterol-lowering drugs, which lower their risk of heart attack. Such a difference could make Avandia look good in comparison to the other drugs.

Comparing it to metformin plus sulphonylurea also is problematic because other research suggests that combination raises the risk of death, Nathan writes in his editorial.

"It's not a study to show that there's not risk" from Avandia, said Michael Kutner, biostatistics chief at Emory University, who had no role in the study.

"It's a leap of faith" for the company now to say that these results suggest the drug is safe, he said.

Avandia had total U.S. sales of $2.2 billion in 2006, slightly trailing $2.6 billion for Takeda Pharmaceutical's competing drug, Actos, according to IMS Health, a health care information company. About 13 million Avandia prescriptions were filled in the U.S. last year. A one-month supply of Avandia sells for between $90 and $170.


On the Net:

New England Journal: www.nejm.org

GlaxoSmithKline: http://www.gsk.com

Glaxo clinical trial registry: http://ctr.gsk.co.uk

Food and Drug Administration: http:www.fda.gov

Avandia's label: http://tinyurl.com/2qzhfe

Diabetes information: www.diabetes.org