A veterinary sedative in street fentanyl: in Canada, medetomidine, used to sedate dogs and cats before surgery, is overwhelming A&E departments, and naloxone does not reverse it

What happened

On 7 November 2026 the Canadian broadcaster CBC published an analysis that was quickly shared among doctors and vets. Emergency physicians across the country say that fentanyl sold on the street is increasingly being cut with medetomidine. It is a powerful sedative from veterinary surgery, and it is changing how doctors save people after an overdose.

What medetomidine is

Medetomidine is a synthetic drug that vets use to calm and immobilise an animal before an examination or surgery. It is not approved for use in people, and its effects on humans have barely been studied. Even so, it has found its way onto the black market because it prolongs and strengthens the effect of opioids.

Why it is added

Fentanyl is the main driver of the opioid epidemic in Canada. Its effect lasts about half as long as heroin's, so dealers add substances that stretch it out. Medetomidine has become one of them. People who buy a dose usually have no idea it contains a veterinary sedative.

How quickly it has spread

Medetomidine was first detected in street drugs in 2023 in Quebec, British Columbia and Ontario. Detections have risen sharply since then, especially in the last two provinces. According to the Canadian Centre on Substance Use and Addiction (CCSA), it is now being found in every province and in Yukon. Saskatchewan and Yukon have seen sharp increases this year.

A record in British Columbia

The first loud warning came in January. On 21 January 2026 paramedics in British Columbia attended 256 drug poisoning calls in a single day, a record for the province. Health officials linked the spike to medetomidine in fentanyl. A similar surge was later reported in Moncton, New Brunswick.

Why patients sleep for longer

Dr Monty Ghosh, an addiction specialist in Calgary, explains the mechanism. Opioids on their own suppress breathing. When medetomidine is added, people become much drowsier, with low blood pressure and a slow heart rate that can last for a long time. Blood flow to vital organs falls, and breathing slows even further.

Naloxone is not enough

The biggest problem for first responders is naloxone. This medicine quickly reverses the effects of opioids, but medetomidine is a sedative, not an opioid. So a person can stay asleep even after naloxone. Philadelphia's public health programme advises focusing on the person's breathing rather than whether they respond.

A new withdrawal syndrome

This autumn researchers in Philadelphia, where the additive has become common, described a new withdrawal syndrome. People used to the mix of fentanyl and medetomidine quickly develop a racing heart, vomiting, high blood pressure and agitated delirium. There have been reports of organ damage. Canadian doctors are seeing the same thing.

How to help in an overdose

The advice for bystanders is still simple: call the emergency services, check whether the person is breathing and support their breathing if needed. Naloxone is still needed, because the mix almost always contains fentanyl. But if the person does not wake up afterwards, it does not mean the medicine has failed: what matters is that they keep breathing until paramedics arrive.

Why it affects everyone

Overstretched emergency departments are not just a problem for people with addiction. When one patient in withdrawal takes up hours of doctors' and nurses' time, everyone else waits longer, from children with injuries to older people with chest pain. That is why doctors are asking the authorities for specialist clinics and more social support.

Intensive care instead of A&E

Dr Sahil Gupta in Toronto says these patients need to be admitted or given intensive care medicines. Breathing and consciousness have to be monitored for much longer than in ordinary opioid withdrawal. In extreme cases some patients are put on a ventilator.

Waiting times and burnout

According to Gupta, this pressure disrupts departments and increases waiting times. Nurses and doctors spend more time with each patient and more beds are occupied. Doctors speak of moral distress among staff: many problems could be dealt with earlier if people had access to help before they ended up in emergency care.

Good news amid the bad

Canada's Chief Public Health Officer, Dr Joss Reimer, notes that opioid deaths fell by 23% in 2025. To bring them down further, she says, coordinated action is needed, especially as emergency services increasingly deal with poisonings from mixtures of substances that need more complex care.

Not the first veterinary drug

Medetomidine is not the first veterinary drug in street drugs. Before it, xylazine spread in the US and Canada and was nicknamed “tranq” because of its veterinary origin. Xylazine does not respond to naloxone either and causes severe skin wounds. Medetomidine belongs to the same group of alpha-2 agonists but is more potent.

Why vets use it

In veterinary medicine medetomidine and the closely related dexmedetomidine are everyday drugs. They are used to sedate an anxious animal before an examination, before X-rays and minor procedures, and as part of preparation for anaesthesia. In animals their effect can be quickly reversed with a specific antidote, atipamezole. There is no approved antidote for people.

Why this matters to vets

Each time a veterinary drug reaches the black market, the rules on storing and recording it get stricter. Practices have to keep sedatives in a locked cabinet, keep registers and check stock. That does not stop animals being treated, but it adds work and can affect the availability of products.

Where the street supply comes from

In the CBC analysis Canadian doctors do not say where the medetomidine on the black market comes from, and they do not link it to vet practices. The quantities involved are large and are spreading across the country. Still, the fact that a veterinary drug has become a common additive is making practices and pharmacies pay closer attention to how sedatives are stored and recorded.

When your pet is sedated

If your vet suggests sedating your dog or cat, there is no reason to worry. At the practice the dose is worked out according to the animal's weight and condition, and breathing and pulse are monitored. Before the procedure tell the vet about all your pet's illnesses and medicines, and ask how long it will take to come round.

After sedation at home

When you collect your pet after sedation, it needs peace and warmth. Sedatives in this group slow the heart rate and lower body temperature. Your pet may be sleepy and wobbly for several hours. Only feed it when the vet says so, and limit stairs and jumping onto the sofa for a while.

Medicines sent home

Some pet sedatives are dispensed for owners to give at home, such as gels for dogs that are frightened of fireworks or thunderstorms. They should be stored as carefully as any strong medicine. A few simple rules help prevent accidents:

1. Keep the product in a closed cupboard out of children's reach.
2. Do not give it to another animal without a prescription.
3. Never use it on yourself or other people in any form.
4. Return leftovers to the practice or pharmacy for disposal.
5. Tell the vet if a pack goes missing.

If a child swallows it

If a child or adult accidentally swallows a veterinary sedative or gets it on their skin, call 999 or NHS 111 straight away. Name the product and have the packaging to hand. Do not wait for the drowsiness to pass: a fall in pulse and blood pressure is dangerous.

Horses and large animals

Sedatives in this group are also widely used in horses and farm animals, where the doses are much higher. Yards and farms that store these medicines should keep them locked away too. That protects both animals and people.

Canada and the rest of the world

Canada and the US were the first to face the medetomidine wave, but experts warn that the black market quickly copies what works. Xylazine has already followed this path: it was first found in North America and then other countries started looking for it. That is why addiction specialists advise keeping an eye on medetomidine early.

What this means for Europe

For European vets the story from Canada is a reminder to keep careful records of sedatives and to think carefully when dispensing medicines for home use. Owners should know which medicines they keep at home and not leave them lying around. For emergency doctors in Europe, Canada's experience is a chance to prepare early for mixtures that naloxone cannot reverse.

When to see a vet

Call your vet if your pet takes longer to come round after sedation than you were told, breathes very slowly or with difficulty, has pale or bluish gums, feels very cold to the touch, vomits or has fits. Seek help urgently too if your pet accidentally eats a medicine meant for it or for another animal.