Doctors and patients should avoid pharmaceuticals that have been on the market for less than three years, according to a Canadian researcher who concluded it regularly takes that long to discover a new drug is unsafe.
In a study published on Tuesday in the journal Open Medicine, Joel Lexchin found that 22 of 528 new drugs Health Canada approved between 1990 and 2010 – 4.2 per cent – were pulled from the market.
Nineteen were pulled because of specific safety concerns; two were pulled because they caused harm that outweighed the benefits.
The median amount of time between the approval of a new drug and its withdrawal was a little more than three years, meaning 11 were pulled in less than three years and 11 in more.
One medication was on the market for 21 years before it was withdrawn.
Health Canada announced last October that nasal sprays containing Calcitonin used to treat osteoporosis in post-menopausal women would be withdrawn because they increased cancer risk.
"Early on, when a drug comes on to the market, we know relatively little about its overall safety profile. That means that both prescribing and taking new drugs can be quite dangerous," said Dr. Lexchin, a professor in the school of Health Policy and Management at York University and an emergency room doctor at Toronto's University Health Network.
"Speaking as a doctor, unless a new drug is a major therapeutic advance, or unless there is nothing else to treat a serious condition, I wouldn't prescribe a drug that's been on the market for less than three or four years."
The study found no major change in the time it took to ban an unsafe drug over the 20-year study period.
It also found drugs are withdrawn in Canada about as often as they are in the United States and Europe. The study showed, however, that the time elapsed between approval of a medication and withdrawal from the market is longer in Canada than in the United States.
No one was available on Tuesday at Health Canada to comment.
Still, Dr. Lexchin argued doctors would be wise to play it safe with new drugs.
"If the drug isn't any better than anything else on the market – and that applies to 90 per cent of the drugs – then we should be using it only rarely. That way we can avoid large numbers of people getting drugs inappropriately. It may take a little longer for the safety signals to build up. But at the same time, we won't harm nearly as many people."