A York University study of drug safety shows that new drugs are often on the market in Canada for more than three years before they are withdrawn as unsafe, raising concerns about turning to the newest drugs available.
The study by Dr. Joel Lexchin, an emergency room physician and professor of the School of Health Policy and Management in York’s Faculty of Health, appeared yesterday in Open Medicine.
“As a doctor my policy is not to prescribe new drugs until they have been on the market for at least three or four years since I don’t know how safe they will be for my patients,” said Lexchin. “Based on the findings in this study, doctors should not prescribe drugs during this period and patients should not take them, unless they are substantially better than existing medications.”
Lexchin found that 4.2 per cent of the 528 new drugs approved in Canada in a 20-year period (from Jan. 1, 1990 to Dec. 31, 2009) were later withdrawn. Of the 22 drugs withdrawn, 11 first had a serious safety warning and 11 did not. The median time between approval and withdrawal was almost three-and-a-half years.
The study examined four 5-year periods and found no difference in the percentage of approved drugs that were eventually withdrawn from the market. This shows that the drug review system’s ability to detect serious safety issues and keep those drugs off the market did not change over the 20-year period, he said, but also raises questions about the rigour of the surveillance system once drugs are on the market.
“There are serious questions about how Health Canada deals with drug safety but we can’t answer these questions because Health Canada will not release the necessary information,” said Lexchin.