Unsafe drugs linger on market, study finds


Decision-making process murky: MD

Unsafe drugs linger on market, study finds

The arthritis drug Vioxx was the 10th-most-prescribed drug in Canada before it was pulled from store shelves.

Photograph by: SPENCER PLATT, GETTY IMAGES FILES , Postmedia News

Dangerous drugs often stay on the market in Canada for more than three years before eventually being pulled from drugstore shelves, new Canadian research shows.

The study, by Dr. Joel Lexchin, an emergency physician and York University professor of health policy, found that about four per cent of new drugs approved by Health Canada between January 1990 and December 2009 were eventually withdrawn for safety reasons. The median time between approval and withdrawal was 1,271 days.


"How is it that you need to issue a serious safety warning within two to three weeks of the drug coming on the market?" Lexchin said.

"What does that say about how well the safety data was scrutinized before the drugs were approved?"

For his study, published this week in the journal Open Medicine, Lexchin compiled a list of all drugs approved between 1990 and 2009 and subsequently withdrawn as of October 2013. The date of approval, the date the first serious safety warning was issued (if one was issued) and the date of withdrawal from the market were recorded for each drug.

Of the 528 new drugs approved during the period, 22 were eventually withdrawn. They included drugs for cholesterol, blood pressure and weight loss, anti-depressants and anti-inflammatories. The drugs were pulled primarily because of cardiovascular risks or liver toxicity.

Of the 22 drugs pulled from the market, 11 had been the subject of a safety warning, and 11 had not.

"Was Health Canada unaware of any safety issues associated with these products before they were withdrawn?" Lexchin writes in Open Medicine.

"And what happens when, within a month of a serious safety warning, it's all of a sudden decided the drug is so unsafe that it shouldn't be kept on the market at all?

"What is the process behind the decision-making? The answer is, we don't know, because Health Canada isn't transparent enough."

It's also not known how many people are exposed to drugs before they are withdrawn, he said. In 2003, the year before Vioxx was removed from the market, it was the 10th-most-prescribed drug in Canada.

For the 11 drugs in Lexchin's study with a prior safety warning, the median time between the warning and withdrawal from the market was 329 days. Two of the drugs - sitaxsentan for high blood pressure and the antiinflammatory valdecoxib - received a safety warning 20 days after approval.

"A lot of new drugs are very heavily promoted to doctors," Lexchin said. "Just as soon as they hit the market, drug companies are trying to ramp up the sales, and that's when people are most vulnerable early on, because that's when we have the least amount of knowledge about drug safety."

Most new drugs are only ever tested in similar groups of patients, Lexchin. "But when there's massive promotion, they get prescribed to all sorts of people they were never tested in."

Lexchin found no change over the 20-year period in the percentage of drugs that are eventually withdrawn for safety reasons, suggesting there has been no improvement in Health Canada's ability to "detect serious safety issues and keep those drugs off the market."

"Unless the drug raises people from the dead, or unless there is nothing else available for that serious medical problem, my advice to doctors and patients is, don't prescribe the drug and don't take the drug until it's been on the market for three or four years," Lexchin said.

"I'm not saying that these new drugs should never be prescribed. But I am saying that they should be used much more cautiously than they are now, (because) if the drugs are heavily prescribed, there can be a large number of people harmed before there is any chance to do anything about it."


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Photograph by: SPENCER PLATT, GETTY IMAGES FILES, Postmedia News


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