One quarter of drivers who were admitted to hospital following vehicle crashes in 2012 had prescription medication in their system.Graeme Roy/The Canadian Press
Data from four of B.C.'s busiest emergency rooms show that a quarter of all drivers injured in collisions tested positive for at least one sedating medication, prescribed or bought over the counter, but the lead researcher says much more work needs to be done to determine the extent such prescription drugs impair those behind the wheel.
Jeff Brubacher, an emergency-room doctor at Vancouver General Hospital and a clinical toxicologist, and a team of researchers found that 26.1 per cent of the 1,097 injured drivers whose anonymous blood samples they tested had taken at least one sedating medication. These drugs were found most frequently in the sample population, followed by alcohol at 17.8 per cent of drivers and cannabis at 12.6 per cent. Cocaine was found in 2.8 per cent of drivers, and amphetamines in just more than 1 per cent.
Dr. Brubacher said his group was most surprised to see 11 per cent of the drivers test positive for the non-prescription diphenhydramine, which is an ingredient in Gravol, a medication to treat nausea and motion sickness.
"I didn't find any numbers as high as that in other studies, so something seems to be going on in B.C. Maybe it's being used as a sleep aid," Dr. Brubacher said. "It definitely causes drowsiness, so it's quite possible that that's a bigger problem than we think – it really isn't on anybody's radar."
The research, done between 2011 and 2012, also detected antidepressants in 6.5 per cent of drivers, and opiates such as Tylenol 3 in 5 per cent.
Tylenol 3 was the most-prescribed drug in B.C. in the 2012 fiscal year, with 114,000 people getting a prescription through PharmaCare to treat pain and fever, according to the latest ministry data.
In Dr. Brubacher's research, 5 per cent of the injured drivers tested positive for benzodiazepines, drugs such as Valium or Ativan that are used as sleep aids or to treat anxiety. Most of the drugs detected in Dr. Brubacher's research have not been studied extensively for their effects on drivers. The most analyzed has been benzodiazepines.
He said the drugs probably raise the crash risk a bit. "[It's] a modest increase, not like alcohol, but it's still something real."
The studies do not take into account how long the person could have been using their prescription, he said.
"It makes a difference how long you've been on these medications. When you first start taking them, that's when you're most likely to have difficulties," Dr. Brubacher said.
Provincial Health Officer Perry Kendall agreed that the extent of the risk posed to drivers by over-the-counter sedating medication and prescription drugs "isn't really known."
"As we're an aging population, and as we tend to be taking more prescription medications for a greater variety of illnesses or underlying conditions, it is a field that should be explored," Dr. Kendall said. "It would be useful to know what medications are associated with increased risk, then it's possible to determine whether that might be causal."
Across the province in the 2012 fiscal year, about 17 per cent of the population got a prescription filled through the provincial program. That same year, the province recorded 30 million prescriptions given to 790,000 British Columbians, almost 18 per cent more claims for about the same amount of people four years earlier.
Dr. Brubacher said the "gold standard" for researching the issue would involve the "really labour intensive" approach of testing drivers who are not involved in crashes to see if sedating drugs are present in the same levels. For now, he wants to compare the injured drivers' insurance records with their prescription histories to look for patterns involving collisions and certain medication.
Mike Hager