The dietary supplement L-arginine continued to be sold in Canada and was used in a clinical trial long after U.S. researchers linked it to six deaths, a CBC investigation has learned.

The amino acid is a hot seller in health food stores across the continent, where it is touted as a natural alternative to drugs for erectile dysfunction and particularly good for the heart.

But it's being pulled off the shelves of Canadian stores pending new labelling, after Health Canada issued an advisory in May warning people who have had prior heart attacks not to take L-arginine.

Ottawa heart surgeon Dr. Marc Ruel had been testing the supplement on volunteers with severely diseased hearts for more than a year before he first heard about the U.S. study, when the deaths were made public in January, CBC Radio News investigators have learned.

 Researchers led by Dr. Steven Schulman of Johns Hopkins University in Baltimore, Md., had been conducting a clinical trial on L-arginine, but stopped it after six participants died.

They concluded that the amino acid might increase the risk of death in patients who have had heart attacks – but didn't publicize the results until 18 months later, in the January 2006 issue of the Journal of the American Medical Association.

Canadian patients not told for months

When he heard about the results of the U.S. study in January, Ruel did not inform his patients because he felt his study was different than Schulman's, which looked exclusively at heart attack patients.

Ruel did not enrol anyone who'd had a heart attack.

"If you look at the Schulman paper, the reason why they stopped the study was because of increased mortality," said Ruel. "Well, in our study so far, we've recruited 20 patients, and all those patients have done well. There hasn't been a single mortality."

Medical ethicist criticizes delay

But Ruel has drawn fire from medical ethicists.

Some of them say people should be told of any information that might influence their decision to enter or continue with a clinical trial.

"If I told you now that another study with this drug had been halted because of excess deaths, is that something you would want to know?" said Dr. Michael Goodyear, who specializes in research ethics at Dalhousie University in Halifax.

Ruel plans to end trial

Ruel said he sent letters to his patients to alert them  to the U.S. findings, asked his data and safety monitoring board whether his trial was safe to continue, and put his study on hold.

However, in early June, Ruel sent an e-mail to the CBC saying he intends to end his study regardless.

 
He said he feared that the CBC's inquiries would result in a controversy he wants to avoid.