The maker of the controversial diabetes pill Avandia on Tuesday published preliminary results of a study that the company claims shows the drug does not raise heart risks. However, experts say the results are inconclusive and even seem to suggest more risk from the drug.

More people on Avandia, or rosiglitazone, suffered heart problems than those on other diabetes drugs — a bad sign even if the difference was so small that it could have occurred by chance alone, some doctors said.

"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.

He wrote an editorial accompanying the study, which was published online by the New England Journal of Medicine.

A congressional panel is holding a hearing Wednesday on the drug's risks and the response by the U.S. Food and Drug Administration, which has been criticized for being too lax about safety concerns.

The heart risk trend in patients on Avandia "is going in the wrong direction," said Dr. Steven Nissen of the Cleveland Clinic.

Two weeks ago, he published in the same medical journal an analysis of 42 studies on Avandia concluding that the drug raised the risk of heart attacks by 43 per cent and possibly heart-related deaths as well.

Avandia's maker, British-based GlaxoSmithKline PLC, has said its own similar analysis found a 31 per cent greater risk.

However, Glaxo officials have said that more definitive studies, such as the preliminary findings released Tuesday, did not show such risk.

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

More than six million people worldwide have taken the drug, sold as Avandia and Avandamet, since it came on the market eight years ago to help control blood sugar in people with the most common form of diabetes.

About one million Americans use it now. IMS Health Canada, a company that tracks drug sales, says more than one million prescriptions for the drug were filled in Canada last year, and Avandia was ranked third in the oral diabetes class of drugs.

The new study involves 4,500 people at more than 150 medical centres around the world.