SARNIA, Ont. - Prescription painkillers, even in small doses, can significantly increase the chances of injury or death behind the wheel, a provincial study says.

Researchers with the Institute for Clinical and Evaluative Sciences found people taking daily doses of opioids, equivalent to 20 milligrams of morphine, increased their risk of collisions by 21% to 42%.

"What's key is making sure the people who are being prescribed the opioids are aware of some of the safety concerns surrounding these drugs," said Tara Gomes, lead author of the first-of-its-kind study: Opioid dose and risk of trauma in Canada: A population-based study.

The study looked at nearly 550,000 cases where patients - ages 18 to 64 - used opioids via a publicly funded prescription between 2003 and 2011.

"In this study we found that even 20 mg of morphine or equivalent can have substantial impacts on your risk of road trauma," Gomes said.

"To me that's very important because there are hundreds of thousands of people across Canada who are receiving opioids at these doses."

"It's just like drinking and driving," said Sarnia Police Const. Shawn Urban. "If you're impaired, you're impaired."

Patients also need to be aware of the risks of driving while on opioids, Gomes said.

"People can avoid driving if they understand that by taking a tablet they may be putting themselves and others at increased risk of being injured when in a car," she said.

The study's findings have the potential to influence doctors prescribing opioids, and legislators who provide public education about the medication, Gomes said.