Every day in Canada, paramedics and bystanders use naloxone, a fast-acting drug that can pull someone back from the brink of an overdose.
But as the street supply grows more toxic, saving a life is getting harder. Increasingly, people require larger doses of naloxone, or receive it multiple times for different overdoses.
“Before, in Alberta, with our naloxone kits, we used to have only two to three vials in each kit,” said Dr. Monty Ghosh, an internist and addiction specialist at the University of Alberta Hospital in Edmonton.
“Now there are four … and in fact, we’re often finding we need to use five or six to get any sort of meaningful effect.”
Medical experts say repeated use of naloxone is medically safe, but more must be done to prevent repeat overdoses.
Rising naloxone use
Naloxone can quickly restore breathing during an opioid overdose. It works by displacing opioids from their receptors, blocking their effects on the brain and nervous system.
In recent years, North America’s synthetic opioid supply has become increasingly toxic, as fentanyl is laced with tranquilizers and nitazenes.
A recent study in the U.S., and earlier studies in Canada, show patients increasingly need more naloxone doses because of this growing potency.
This toxicity has led to an “endless recurrence” of overdoses in the same individuals, Marc-André Périard, vice president of the Paramedic Chiefs of Canada, told Canadian Affairs in June.
Some first responders worry about the effect of administering naloxone repeatedly.
“One of the … senior paramedics that works in our team said naloxone is like a fire extinguisher,” said Keith Johnson, the acting deputy chief of the Edmonton Police Service.
“The maximum [dose of naloxone] itself will bring people back, but what’s the effect [that] it has on a person over numerous administrations?”
There are no published studies on the long-term effects of repeated naloxone use. But medical experts told Canadian Affairs naloxone is overwhelmingly safe.
“The half-life is not very long — it’s quickly metabolized, and it’s quickly excreted,” said Ghosh, of the University of Alberta Hospital.
Most side effects — “hot flash-type feelings, abdominal cramps, muscle spasms” — are mild and common, says Ghosh.
The clinical literature shows naloxone can, in rare cases, cause noncardiogenic pulmonary edema — fluid buildup in the lungs and a cough that produces “pink, frothy sputum.” But it is difficult to know whether this is caused by naloxone or the opioid itself.
“One of the hallmark signs of an opioid overdose would be when you find someone who is unresponsive … [and] you see foam around their mouth,” said Dr. Jessica Kent-Rice, an emergency medicine physician at St. Michael’s Hospital in Toronto.
“Naloxone cannot be causally linked to these things … because we can’t really tease out if it’s naloxone that’s causing it, or if it’s the opioid. And it’s probably the opioid.”
Sources also noted that withholding naloxone would pose a far greater risk than providing someone with multiple doses.
“The only way to restore that breathing [in an opioid overdose] is by giving naloxone,” said Kent-Rice, who is also a medical toxicologist and coroner.
“I have no hesitation with giving naloxone to pretty much anybody,” she added. “It’s just the dose that we try to [adjust].”
‘No incentive to stop’
Ready access to naloxone may encourage riskier drug use, some critics of harm reduction policies have said.
“There’s no incentive for them to stop,” reads a Feb. 25, 2025 post on X from an anonymous political critic from Saskatchewan. “Eliminate safe supply, dismantle safe injection sites and stop publicly funding naloxone kits.”
But a 2020 U.S. study found broader access to naloxone did not increase the likelihood of repeat overdoses.
In Canada, a government report on emergency visits for opioid-related harms found repeat visits rising over time; the report concludes this rise is likely due to gaps in follow-up care rather than naloxone use.
Sources said overdose reversals can be critical opportunities to assist individuals with seeking treatment.
“[Naloxone is] not going to treat someone’s opioid use disorder,” said Kent-Rice. “That’s just going to keep them alive long enough that hopefully you can engage them in treatment.”
A November 2025 study by Kent-Rice and researchers at the University of Toronto and Unity Health Toronto found nearly a quarter of hospital-treated opioid overdoses recurred within six months. Starting opioid agonist therapy immediately after hospitalization cut that risk in half, the study said. Opioid agonist therapy uses medications to reduce withdrawal, cravings and the risk of overdose.
“Any touch point with the healthcare system … represents an important opportunity to offer support and help make connections to treatment,” Shaleesa Ledlie, a lead researcher in the study, told Canadian Affairs in an email.
“Given the evidence surrounding the effectiveness of opioid agonist treatment in reducing the risk of repeat toxicities, this could represent a potentially life saving intervention.”
