A powerful veterinary sedative is being added to street fentanyl — and ERs are struggling to cope

Emergency physicians across Canada say a powerful veterinary sedative is being added to fentanyl sold on streets, complicating their response to overdoses as they juggle patients.

Medetomidine, a synthetic sedative, is used in veterinary surgery and has not been approved for use in humans, nor have its effects on people been well studied. The effect of fentanyl, a key driver of the opioid epidemic in this country, lasts half as long as that of heroin; adulterants like medetomidine are taken to extend it.

The synthetic was first detected in 2023 in Quebec, B.C. and Ontario, with detections increasing substantially in the latter two provinces since then, according to a report from the Canadian Centre on Substance Use and Addiction (CCSA). It has also been found in the Maritime region, and Saskatchewan and Yukon have seen sharp increases this year.

This fall, researchers in Philadelphia, where the additive has become common, flagged that physicians were reporting a "novel withdrawal syndrome" among those with opioid use disorder living in areas with a high level of medetomidine in the drug supply. Symptoms of the condition, which can develop quickly, include a severely elevated heartbeat, vomiting, hypertension, agitated delirium and even reports of organ damage.

Now, Canadian overdose prevention workers and emergency physicians are struggling to deal with it, too. They also report difficulties in treating medetomidine withdrawal, which can lead to complications like heart attacks or strokes from the blood pressure, said Dr. Monty Ghosh, a Calgary-based addictions physician and researcher.

"These are the things that we kind of have to match that we didn't have to match before," Ghosh said. "It's sort of skewed our management strategies for these individuals."

WATCH | Canada's toxic drug supply evolves:

Drowsy patients coupled with heart attack risks

Taking opioids can make it difficult for a person to breathe. Add in medetomidine, said Ghosh, and they'll also become much drowsier, with low blood pressure and a low heart rate that can stay down for long periods of time.

"It can be very dangerous," he said, because that reduces blood flow to vital organs, which can lead to serious complications, as well as slow breathing.

At overdose prevention sites in B.C. and Montreal, nurses also say they're concerned about users having very low heart rates and becoming dizzy and unresponsive for hours, according to a CCSA presentation. Regularly monitoring a person's pulse, heart rate and oxygen levels now matters more, because these changes can be delayed compared with previous drugs and adulterants.

When reversing an overdose where medetomidine is involved, Substance Use Philly noted it is important to focus on the person's breathing rather than their responsiveness, given that medetomidine is a sedative and therefore does not respond to naloxone, which reverses opioid overdoses.

Medetomidine withdrawal, meanwhile, can come on quickly and brings its own set of problems, like the question of how much vomiting is too much.

Dr. Sahil Gupta, who works in Toronto, says patients experiencing medetomidine withdrawal require hospitalization or intensive care medications because breathing and consciousness need to be monitored for a longer period of time than with opioid withdrawal.

"In our emergency departments, [these] patients take a longer amount of time, both from a nursing, staff physician and time within the hospitals" perspective.

• Opioid deaths dropped 23% in 2025 — bringing 'cautious optimism' from Canada's top doctor

While the goal is to support breathing to prevent the brain from starving of oxygen, in extreme circumstances, patients will need to be put on a ventilator, he said.

A box of Narcan sits at a community outreach storefront in Philadelphia in 2023. Generically known as naloxone, the medication used revive people who have stopped breathing doesn’t reverse the effects if opioids are absent. (Matt Rourke/The Associated Press)

"[Resource] strains like this tend to actually create a lot of disruption and cause increased wait times, overcrowding," Gupta said. "Often the patients experiencing the medetomidine withdrawal are requiring hospitalization or intensive care meds, as well, which are much more high-resource areas." 

Gupta said unless the whole continuum of homelessness and socioeconomic factors are addressed, "we're really not going to make inroads." 

Proposed solutions

One doctor in Alberta helped create a program meant to try and address emergency room overcrowding.

The Edmonton program, called Bridge Healing, looks to address homelessness among those making repeat hospital visits, said Dr. Louis Hugo Francescutti, a professor in the School of Public Health at the University of Alberta who works as an emergency physician.

If someone comes to the emergency department with no fixed address, Francescutti said they're asked two questions: whether they are homeless, and whether they want a chance to get their life together again.

• What Canada's wastewater reveals about drug use in 8 cities

• Province says consumption site improving safety, but some businesses disagree

"If they say yes and there's beds available, we send them by cab to these purpose-built buildings, where we provide them free-of-charge accommodation," he said, along with services including access to a medical clinic to start to address their needs.

"Emergency department staff are becoming morally distressed," he said. "They're burning out because they see a problem that is solvable if we had the right people intervening."

He said that includes better access to specialized clinics and practitioners like social workers.

WATCH | Hospitals & housing:

However, some practitioners say there is another missing element: safe consumption sites, many of which were closed down in provinces like Ontario, with the provincial government saying the sites encouraged drug use.

• Toronto hospital to greatly expand permanent housing program that reduces ER visits

At these sites, workers would be able to assess comatose overdose patients, potentially giving them oxygen or a small dose of naloxone so they can avoid being put into full opioid withdrawal, said Dr. Raghu Venugopal, an emergency physician at three downtown Toronto hospitals.

"This really matters because if you want safe subways, if you want safe parks, if you want a better-functioning ER, there is a place for people who need to use drugs," he said.

Indeed, without the supervised sites, people who previously would have been revived at the sites now need to go to emergency, a 2026 report by Gillian Kolla of Memorial University's medicine faculty and epidemiologist Tara Gomes of the Ontario Drug Policy Research Network suggests, delaying care for other life-threatening conditions such as heart attacks and traumatic injuries from vehicle collisions.

Asked to respond to the emergency physicians' calls, Ontario's Health Ministry pointed to its approach. 

"Instead of giving people tools to use harmful, illegal drugs, our government is helping people break the tragic cycle of drug addiction by making record investments in more mental health and wraparound supports," Lily Barnes, a spokesperson for Ontario's health minister, said in an email.

"Across the province, we are investing a historic $560 million to build 29 Homeless and Addictions Recovery Treatment (HART) Hubs, including 4 in Toronto, replacing the failed approach of drug injection sites."

Barnes said Ontario's 29 HART hubs are open to set people on a path to recovery, with each hub receiving four times more funding than the drug sites.