Veterinary tranquilizers found in majority of Toronto fentanyl samples: drug testing service

Veterinary tranquilizers are being found in a large amount of downtown Toronto's fentanyl supply, according to a drug testing service.

Between Feb. 22 and March 7, toxic drug samples taken by Toronto's Drug Checking Service, a free and anonymous public health service that collects toxic drug samples for testing from 10 sites around the city's downtown, found 81 per cent of what users expected to be fentanyl included xylazine and medetomidine.

It's a dangerous mix, says Hayley Thompson, the managing director of Toronto's Drug Checking Service.

"Both of these are veterinary tranquilizers that are central nervous system and respiratory depressants that, particularly in combination with high potency opioids like fentanyl, would work to suppress people's vitals," Thompson said. 

It's not entirely clear why these tranquilizers are added to fentanyl, but Thompson says she believes it is to sustain the short-acting opioid's effect for a longer period of time. 

Thompson says seeing fentanyl combined with veterinary tranquilizers, especially xylazine, isn't new, but the drug checking service hasn't seen numbers like these since it started testing samples in 2020.

The presence of these tranquilizers adds multiple health risks, front line workers say. 

For instance, Thompson says naloxone, which reverses the effects of fentanyl, doesn't reverse the effects of veterinary tranquilizers.

Frontline worker Sarah Greig says she suspects the mix of tranquilizers and fentanyl is also behind a rise in paramedic calls related to cardiac arrests at the Moss Park Consumption Treatment Service over the past few months. 

Greig, director of substance use and mental health at South Riverdale Community Health Centre, says supervised consumption sites aren't equipped for that.

"Our sites are set up to respond to opioid overdoses or respiratory issues," Greig said. "We're not set up for cardiac issues."

According to data provided by Ontario's chief coroner, Dirk Huyer, the presence of xylazine in opioid-related deaths didn't change much from 2023 to 2024, going up only 3.6 per cent.

Huyer says Toronto's Drug Testing Service has the more relevant numbers for the moment, since coroner data only comes in well after someone has died. 

"It's really, I think, the most effective way to understand what's happening now," he said.