Calgary police patrol the streets near the city's drug safe injection site, February, 2019.Todd Korol/The Globe and Mail
People who survived an opioid overdose are at greater risk of premature death and of overdosing again after being released from hospital than previously thought, according to new research from Ontario that highlights the impact of fentanyl in the illicit drug market.
The study, published in the Journal of the American Medical Association on Thursday, noted that studies conducted before the emergence of fentanyl found much lower estimates of death and repeat overdose. Fentanyl has dominated Canada’s drug supply since 2016, killing tens of thousands.
Based on patient data from 2017 to 2023, researchers concluded that nearly 9 per cent of individuals died and 21 per cent had at least one more overdose in the year after an emergency department visit for a non-fatal opioid overdose. Previous studies conducted before the fentanyl era had mortality postoverdose estimated between 5.3 per cent and 5.5 per cent, the study noted.
Lead author Robert Kleinman, a clinician-scientist at the Institute for Mental Health Policy Research at the Centre for Addiction and Mental Health in Toronto, said the risk is particularly high in the seven to 30 days after hospital discharge.
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Within one week, 0.6 per cent of individuals died and 2 per cent experienced a repeat overdose. Within 30 days, 2 per cent died and 6 per cent overdosed again.
“But it remained high throughout the year. And people who had a prior overdose in the preceding five years were at an even higher risk of death,” Dr. Kleinman said. “These elevated, early postdischarge risks highlight the importance of ensuring that interventions, like opioid agonist treatments and take-home naloxone, are available and accessible.”
Opioid agonist treatments help to reduce cravings and withdrawal symptoms, while naloxone is fast-acting medication that can reverse the effects of an opioid overdose. Access to these treatments varies across Canada, with particular barriers in rural and remote regions.
Nearly 52,000 people have been hospitalized for opioid poisonings in Canada between January, 2016, and September, 2025, based on national data. The latest figures cover the first nine months of last year, during which 3,613 hospitalizations were reported.
Roughly a quarter of those hospitalizations, or 24 per cent, involved fentanyl or its analogues, which are synthetic opioids that share a similar chemical structure. The drugs’ share of the total has increased by 50 per cent since 2018, when national surveillance began, but appears to have stabilized in recent years.
Dr. Kleinman said further research is needed to improve interventions in hospitals to limit the risk of injury after being discharged. One example at CAMH is having people with clinical expertise in addictions present in the ED, which he said allows for the rapid initiation of medications for opioid-use disorder.
More than 55,000 Canadians have died from opioid poisonings since 2016. While drug deaths have steadily declined in Canada over the past two years, there are significant disparities in pockets of the country where deaths continue to mount, including in Edmonton.
The new study was conducted using data from nearly 28,500 people in Ontario. These individuals visited an emergency department between 2017 and 2023 for a non-fatal overdose, from either illicit or prescribed opioids, and were aged 15 and older, the average age being 39. The data came from ICES, a non-profit Ontario research institute.
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Dr. Kleinman said one limitation of their research was that it focused on people who were discharged from the ED and did not include those who were admitted to hospital. Nor did they look at people who non-fatally overdosed in the community and did not receive hospital care.
“So we think that rates of opioid overdose are actually higher than what we’ve identified,” he said, which “suggests that people who have an opioid overdose are actually at an even higher risk of repeat opioid overdose over the following year than our paper would suggest.”
Dr. Kleinman said he hopes this study is the first step of many to evaluate the risks of overdose and identify tailored supports to help this high-risk population.