Two physicians who tried to warn about the high risk of serious side-effects of the Type 2 diabetes drug Avandia allege they were intimidated by the company that sells it, a CBC investigation revealed Wednesday.

Last year, a review published in the New England Journal of Medicine found a 43 per cent higher risk of heart attack among people taking Avandia, or rosiglitazone, compared to a control group, and 64 per cent more likely to die of cardiovascular problems.

Avandia was hailed as a breakthrough for blood-sugar control. It is designed to help sensitize the body to insulin.

Both the U.S. Food and Drug Administration and Health Canada have issued strong warnings as a result of the 2007 study. By that point, researchers were estimating thousands of people taking Avandia had died, given it had been on the market since 1999. In Canada in 2007, doctors had written more than a million prescriptions for Avandia, according to IMS Health Canada, an industry trend watcher.

In 2000, Dr. Mary Money, an internist from Hagerstown, Md., raised one of the earliest alarms about Avandia. Of 33 patients she put on the new drug, 20 went on to develop serious edema, or fluid retention — a symptom of heart failure.

"Well over half of them were developing this fluid retention with the medication," Money recalled.

'I felt intimidated,' endocrinologist says

Money started warning colleagues and other hospitals about the effect, and sent reports to the FDA and the drug's manufacturer, SmithKline Beecham, now known as GlaxoSmithKline.

Company officials met with Money about their concerns. They then wrote a letter to her boss at Washington County Hospital, asking him to stop her from "disseminating misinformation about a useful medication" because the company was concerned other doctors were becoming reluctant to prescribe it.

Money said she was afraid the company would sue her for slandering their drug.

Dr. Stephen Lippman is an endocrinologist who helped Money investigate the side-effects.

"I felt intimidated; I know she felt intimidated," Lippman said. "We both at the time, and still do, think that they were essentially trying to stonewall us and really impede a resolution of the issue."

Lippman said they both felt frustrated by the way the company described them to the hospital's chief of staff.

"We were basically country bumpkins who didn't know how to investigate this stuff," said Lippman, a physician who holds a doctorate in molecular biology.

The chief of staff at the time said he trusted Money

A U.S. Senate committee is investigating how widespread the alleged bullying of doctors might be, and is expected to release its report soon.

No complaints received in Canada, company says

GlaxoSmithKline declined an interview. In an e-mailed statement, the company said:

"GSK does not condone any actions that would interfere with an individual's ability to discuss, report or publish adverse events related to any GSK product. As a corporation, we actively train all employees on ethical business practices and compliance with the Rx&D Code of Conduct," an industry group that represents brand-name pharmaceutical companies in Canada.

"GSK Canada is not aware of any complaints filed as a result of alleged inappropriate interactions with health-care practitioners in this regard."

On Wednesday, the company added: "There is a fundamental difference between engaging in scientific debate to ensure the accuracy of public statements, and attempting to intimidate. GSK has a responsibility to correct inaccuracies regarding its medications for the benefit of physicians, patients and scientific discourse. That is precisely what happened here."

Drug companies attempt to silence doctors and critics in Canada as well, alleges Arthur Schafer, a medical ethicist at the University of Manitoba.

"Threats of lawsuits or threats to go to your employer or actually going to your employer to get you fired or disciplined or silenced in some way are unusual," said Schafer. "They happen, but usually for the drug companies, the carrot is more effective than the stick."

The carrot comes in the form of research grants for hospitals and universities, and lucrative consulting contracts for doctors, Schafer said.