Carfentanil is a high-potency opioid, considered to be up to 100 times stronger than fentanyl.
Since Toronto’s Drug Checking Service launched in 2019, we’ve observed carfentanil fade in and out of Toronto’s unregulated fentanyl supply.
Over the past few months, we’ve been finding carfentanil more often – and not only in fentanyl samples collected in Toronto, but also in fentanyl samples collected in Kingston, Peterborough, and Thunder Bay (the other 3 jurisdictions that currently participate in our provincial public health program, Ontario’s Drug Checking Community).
Similar trends are being observed elsewhere in Ontario, Canada, and the United States.
In August, we found carfentanil in 14% (18) of the fentanyl samples collected in Toronto. That’s the most we’ve seen in a month to date.
Carfentanil is generally found in combination with other high-potency opioids (opioids considered to be as strong as or stronger than fentanyl), as well as with other central nervous system and/or respiratory depressants, like benzodiazepine-related drugs and veterinary tranquilizers (xylazine, medetomidine).
Of the 179 samples collected in Toronto that contained carfentanil between October 2019 and August 2025:
- 88% contained at least one other high-potency opioid
- 62% contained at least one benzodiazepine-related drug or veterinary tranquilizer
Using carfentanil may:
- Result in overdose
- Lead to dangerous suppression of the vitals, including slowing down of breathing, blood pressure, heart rate
- Make responding to an overdose more challenging
These risks and challenges are increased when…
- Carfentanil is used unknowingly
- The amount of carfentanil used is unknown
- Carfentanil is unknowingly used in combination with other high-potency opioids, central nervous system and/or respiratory depressants
…which are almost always the case given the extreme contamination and unpredictability of our unregulated fentanyl supply.
Review our tips and help to reduce the harms associated with using drugs from an unregulated supply.
We are continuing to monitor this trend and will keep the community informed as we learn more. To interact with our data, visit www.drugchecking.community.