There are “many limitations” to how drug safety and effectiveness is monitored and reported in Canada and “vast improvements” are needed, says a new report.

Over the past 25 years, the percentage of drugs withdrawn from the market has not changed, but the number of people exposed to unsafe drugs has been increasing, says the study, which is published by the independent Health Council of Canada.

For example, two of the five most heavily-promoted drugs in Canada in 2000 and which were widely prescribed - Bayer’s cholesterol-lowerer Baycol (cerivastatin) and Merck & Co’s arthritis and pain relief treatment Vioxx (rofecoxib) - were withdrawn because of safety issues. Between 1999 and 2004, when Vioxx was removed from the market, about 16 million prescriptions had already been written for it, the study notes.

Moreover, Canadians are not informed of the safety concerns about drugs that are currently on the market, it says. “People often think that since a drug has been approved by Health Canada, it is safe,” says the Council’s chief executive, John Abbott. However, he adds: “what Canadians don’t know about are the limitations in our current pre-market testing and the lack of surveillance once a drug has entered the market.”

Although mandatory, pre-market testing by drugmakers is limited in scope, say the authors, while the “current random nature” of post-marketing surveillance is the result of a lack of regulatory requirements that compel manufacturers to conduct additional research on product safety and effectiveness once their drug has entered the market.

“Health Canada has limited authority to deal with post market safety issues,” comments Joel Lexchin, a professor at York University’s School of Health Policy and Management, and one of the lead authors of the paper. “Health Canada cannot require companies to conduct post-market studies or change drug labels after the product has been approved unless significant new safety issues have been identified. And although it has the authority to order drugs to be withdrawn from the market, they rarely exercise this power,” he says.

In its recommendations on how a comprehensive drug safety system should be developed for Canada, the report points out that the country’s Drug Safety and Effectiveness Network is in the early stages of development, having only been created in 2009.

The authors recommend that: - post-market researchers should have access to data from all sources; - post-marketing research required by Health Canada should be registered, unbiased, transparent and free from conflicts of interest and that it should follow guidelines;  - Health Canada should be given legislative authority to impose penalties for failure to complete post-marketing safety studies; - all required post-marketing studies should be made public; and - all researchers and committee members should submit conflict-of-interest disclosures.

There also needs to be: - adequate and ongoing funding for the system; - better communication of drug safety messages, with wide dissemination; - monitoring and evaluation of drug safety messages; and - broad stakeholder involvement in decision-making concerning publicly-commissioned post-marketing studies, they add.