New animal tranquilizer detected in Toronto's unregulated drug supply

New animal tranquilizer detected in Toronto’s unregulated drug supply

A new, highly potent veterinary tranquilizer is circulating in Toronto’s unregulated drug supply.

The development was reported by Toronto’s Drug Checking Service (TDCS), a free and anonymous public health service offered at five harm reduction agencies in the downtown core.

According to TDCS, a substance known as medetomidine/dexmedetomidine was detected for the first time in the city on Dec. 29, 2023.

Discovered at the Centre for Addiction and Mental Health’s Clinical Laboratory and Diagnostic Services, technicians used a process called liquid chromatography–Orbitrap high resolution mass spectrometry to identify this surgical anesthetic/sedative and analgesic.

Medetomidine is a tranquilizer approved only for use on animals, while dexmedetomidine is approved for use on both humans and animals for sedation and pain relief.

Both of the medications have very similar chemical structures and are being reported together because TDCS is not currently capable of differentiating between the two in lab tests, it said in a Jan. 29 bulletin.

The service said that it is also working with its partners at St. Michael’s Hospital – Department of Laboratory Medicine to ensure that this new drug is also identified using other lab technologies.

This tranquilizer is actually the second substance of this kind that has been unexpectedly found in Toronto’s unregulated drug supply.


In October 2020, a similar animal tranquilizer called xylazine was found to be circulating in Toronto.

Medetomidine/dexmedetomidine is stronger than xylazine, which is sometimes referred to as “tranq,” “tranq dope,” or “horse tranquilizer,” as it is longer acting and produces a greater sedation.

This new drug can put users in a deep state of unconsciousness especially when consumed in combination with high-potency opioids, benzodiazepine-related drugs, and xylazine.

It can also cause a decrease in blood pressure and heart rate and may slow down breathing.

The effects of medetomidine/dexmedetomidine consumption cannot be reversed with naloxone as these drugs are not opioids. Naloxone will, however, work to reduce on any opioids that may be present in the drug cocktail and are contributing to an overdose.

Toronto’s Drug Checking Service, which is also known as the centre on Drug Policy Evaluation, said that between Dec. 29, 2023, and Jan. 23, 2024, medetomidine/dexmedetomidine was found in 11 per cent (15/140) of the expected fentanyl samples it checked. The samples were collected in the city’s west end and in the downtown core and are blue, green, grey, orange, purple, and white.

The service said that this finding is notable as 100 per cent of the samples found to contain medetomidine/dexmedetomidine also had at least one high-potency opioid.

“About half of these samples were reported as being strong and/or associated with drowsiness and sedation and/or dizziness/nausea/vomiting,” TDCS said.

“Much like xylazine and benzodiazepine-related drugs, we suspect medetomidine/dexmedetomidine is being added to unregulated fentanyl to mimic or enhance the sedative and euphoric effects of the opioid a person is choosing to use.”

Both drug checking services in Victoria, British Columbia as well as Health Canada’s Drug Analysis Service have identified medetomidine/dexmedetomidine in the unregulated drug supply. This substance has also been detected in the United States.

Toronto’s Drug Checking Service, which was launched in October 2019, aims to reduce the harms associated with substance use and, specifically, help prevent overdose by offering people who use drugs timely and detailed information on the contents of the unregulated substances they choose to consume.