09/21/2011 05:21 EDT | Updated 11/21/2011 05:12 EST

Benefits outweigh risks: Health Canada lets clotting drug back on market

TORONTO - A controversial clotting drug pulled from sale in Canada and abroad several years ago is being allowed back on the Canadian market.

Health Canada announced Wednesday it is letting Bayer Inc. resume sales of aprotinin, marketed under the brand name Trasylol.

The company agreed to suspend sales of the drug in the fall of 2007 after a Canadian-led clinical trial comparing it to two other clotting drugs was stopped early by its independent safety monitoring board. All clinical trials have a board of uninvolved experts who review the data on an ongoing basis to ensure patients aren't being harmed.

The safety board had seen evidence of higher rates of death among patients in the aprotinin arm of the BART trial, which was led by researchers at the Ottawa Health Research Institute.

The results were later published in the New England Journal of Medicine. In the wake of the study, Bayer withdrew the drug from a number of markets around the world. The drug remains off the market in some, including the United States.

"After careful review, Health Canada has concluded that the benefits of Trasylol outweigh the risks when Trasylol is used as authorized by Health Canada," the department said in a statement.

"Health Canada concluded that the (BART) study was not designed to reliably determine the risk of death ... relative to the two drugs it was being compared against, and that the increased number of deaths in Trasylol patients could have been due to chance."

One of the co-principal investigators of the BART trial questioned the decision, saying he and his team stand by their findings.

"What we did and what we found — not changed," Dr. Paul Hebert said when reached in Ottawa.

Hebert said he and colleague Dr. Dean Fergusson, the other study lead, were called to give evidence at closed-door hearings where Health Canada reviewed the drug's safety.

"The truth is it's a very expensive drug that was being used with the thought that it prevented massive bleeding. We said 'You know, what? ... Yes it prevents a little bit of massive bleeding, but it causes an excess mortality of two per cent.' So in the population we studied there was no evidence of benefit."

The statement said Health Canada concluded that the drug's benefits outweigh any risks when used as authorized. And Health Canada and Bayer have agreed on a boxed warning that will be added to the product label to emphasize that the drug should only be used as authorized.

Hebert said that statement points to basic problem.

The drug is authorized for use in low risk cardiac bypass surgery. That type of surgery, called coronary artery bypass graft, is known in medical shorthand as CABG.

But aprotinin came to be used in higher risk surgery, because of its perceived increased ability to prevent dangerous blood loss in those settings. And it was in those patients where the BART trial saw the increased risk of death.

The Health Canada statement said it has asked Bayer to conduct further studies to determine whether aprotinin is safe and effective in higher risk cardiac surgeries. It said it will monitor the drug closely.