Drivers who have taken even a small dose of opioid painkillers have an increased risk of being injured in a car accident, a new study has found.
Among adult drivers prescribed opioids, a daily dose exceeding only 20 mg morphine (or equivalent) was associated with between a 21 per cent and 42 per cent increased risk of road trauma requiring a visit to an emergency department, the study found.
The study, published today in the journal JAMA Internal Medicine, was lead by Tara Gomes, a scientist at the Institute for Clinical Evaluative Studies. Gomes recently joined the Li Ka Shing Knowledge Institute of St. Michael's Hospital.
Gomes said it was the first study of its kind to demonstrate a relationship between the dose of opioid analgesics and risk of road trauma.
The study examined 549,878 patients ages 18 to 64 who received at least one publicly funded prescription for an opioid between April 1, 2003, and March 31, 2011, in Ontario. Opioids are drugs such as morphine, codeine or oxycodone used to relieve moderate to severe pain.
Road trauma and the toxic effects of prescription drugs are two of the leading causes of accidental death in North America.
"Among drivers prescribed opioids, a significant relationship exists between the dose of opioid prescribed and risk of road trauma," said Gomes.
High opioid doses (between 100-199 mg of morphine or equivalent) were associated with a 42 per cent increased risk of road trauma relative to low doses.
"Injury and death resulting from motor vehicle collisions have significant public health and economic consequences," Gomes said. "These findings could have important implications for clinicians when escalating patients to high opioid doses, and to policy makers tasked with educating the public on the potential risks of opioid medications."
Clinical guidelines recommend about 180-200 mg of morphine or the equivalent as "upper dose thresholds."
Gomes is also the lead scientist for the Ontario Drug Policy Research Network, a province-wide network of researchers who provide timely, high-quality advice for decision-makers.