Health Canada waited to pull a pain drug off the market until U.S. officials made the decision to recall it, a move sparking criticism of the government's ability to act independently to protect the safety of Canadians from potentially dangerous medications.
Health Canada and Paladin Labs Inc. announced a recall Wednesday of Darvon-N, the brand name of dextropropoxyphene, also known as propoxyphene, after new research showed the drug is linked to serious abnormal heart rhythms. The announcement came less than two weeks after the U.S. Food and Drug Administration decided the drug should be removed from the market.
But widespread safety concerns about the drug have actually been around for decades, and prompted Britain and the European Union to ban Darvon-N amid fears it was linked to suicide and accidental overdose.
Public Citizen, a U.S. advocacy group that has been calling for the removal of Darvon-N from the market for years, has been critical of the drug's efficacy, saying there is little evidence it is effective at managing pain.
Despite these concerns, Health Canada opted not to take action on Darvon-N until the department's U.S. counterparts ordered it off the market in November.
Sylvie Ducharme, director of regulatory affairs at Paladin Labs, which manufactures Darvon-N in Canada, said the company approached Health Canada with its decision to withdraw the drug from the market, and the department agreed.
Joel Lexchin, a professor in the School of Health Policy and Management at York University in Toronto, said Health Canada should have taken an active role with respect to Darvon-N, as well as other drugs. The department's follow-the-leader behaviour exposes major shortcomings and weaknesses in its drug monitoring capabilities, he said.
"This drug should have been off the market 30 years ago," Dr. Lexchin said in an interview Thursday. "Unfortunately, it took this long to get it off the market."
Health Canada said it has been monitoring the safety of the drug and contacted Paladin Labs when it learned of the FDA decision. Gary Holub, a departmental spokesman, added that action wasn't taken before because evidence suggested the drug was safe. That changed when research was published linking Darvon-N to abnormal heart rhythms.
The number of patients taking Darvon-N has been steadily decreasing in recent years, as new pain drugs have emerged. In 2005, nearly 40,000 prescriptions for the drug were dispensed in Canada, according to IMS Brogan, a company that tracks the pharmaceutical industry. Last year, that number had dropped to just under 22,000.
Dr. Lexchin said it's troubling that the drug was allowed to remain on the market despite the fact it can cause serious health problems. It demonstrates that not enough safety studies are being conducted when new drugs emerge, and could suggest that other older, seemingly safe drugs, may not be so innocuous, he said.
"Just because they've been on the market for 40 years … doesn't mean they don't have potentially serious side effects," Dr. Lexchin said. "If we don't look for them, we're never going to find them."
Health Canada should beef up its system for monitoring the safety of drugs as well as tracking the number of patients who experience serious side effects, he said.