Potent animal tranquilizer found in Toronto's street drug supply for 1st time

A drug testing service in Toronto says it has detected a new, highly potent animal tranquilizer circulating in the city's unregulated drug supply. 

Toronto's Drug Checking Service (TDCS), a free and anonymous public health service offered at five harm reduction agencies, said in a Jan. 29 alert that it first identified a substance that is either medetomidine or dexmedetomidine late last month. 

"Both are used to put either animals or people into deep states of sedation and we are finding this drug or drugs in the unregulated fentanyl supply," said TDCS manager Hayley Thompson.

"[These drugs] repress the nervous system and respiratory system, putting people at greater risk of both fatal and non fatal overdose."

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

In total, the service detected the substance in 15 out of 140 samples it tested between between Dec. 29 and Jan. 23. All of the samples were taken in downtown or the west end and were thought to be fentanyl . The two anesthetic drugs have very similar chemical structures and are being reported together because the service can't currently differentiate between them, TDCS said.

The discovery highlights how new, dangerous additives continue to show up in Canada's highly toxic drug supply, putting people who use drugs at higher risk of overdose and other negative health effects.

WATCH | Street drugs being laced with toxic animal tranquillizer xylazine:

More than 500 people died of opioid overdoses in Toronto in 2022, according to the latest city data. However, a Public Health Ontario report last year showed people in Ontario are increasingly dying with multiple toxic drugs in their system.

CBC News has previously reported on how xylazine, a severely potent veterinary sedative, is being cut with opioids like fentanyl to prolong their effects.

Xylazine is typically used to sedate large farm animals such as cattle and horses, but the tranquillizer is not approved for use in humans in Canada and its long-term effects on human health are unknown.  As a central nervous system depressant, it dangerously suppresses vital signs like heart rate and blood pressure.

When mixed with fentanyl, it's known as "tranq" or "zombie dope," and can cause hours-long blackouts and horrific, painful wounds that can lead to amputation. 

A March 2023 report from Health Canada showed the rapid spread of xylazine across the country during the past few years, with a growing number of street drug samples seized by law enforcement agencies testing positive for the tranquillizer — overwhelmingly in Ontario.

Medetomidine and dexmedetomidine are even more potent than xylazine because they are longer acting and produce greater sedation, TDCS said.