Detection of Potent 'Nitazene' Synthetic Opioids by a networked drug checking service in Toronto, Ontario, Canada

Wednesday, 23 November, 2022 - 15:00 to 16:30


Background: Amidst an ongoing overdose crisis and COVID-19 pandemic, new psychoactive substances are being detected in unregulated drug markets across North America. We report on the initial detection of potent synthetic opioids of the benzimidazole class, colloquially known as 'nitazenes', in Toronto, Canada via a networked drug checking service (DCS) during a period of heightened COVID-19 restrictions and overdose mortality.

Methods: The substance and drug administration equipment samples presented were submitted anonymously and without charge to frontline harm reduction agencies participating in Toronto’s DCS from February-August 2021. Analyses were conducted in two clinical laboratories using liquid or gas chromatography mass spectrometry. Laboratory analyses are supplemented by surveys completed by service users or partner agency staff.

Results: Overall, 1672 samples were checked during the study period, including 928 (56%) of samples expected to contain fentanyl, heroin, carfentanil, or where the expected drug was unknown. Among those samples, nitazenes were detected in 73 (8%); none were detected in samples expected to be stimulants, benzodiazepines, or psychedelics. The following nitazenes were identified: metonitazene (n=38/73, [52%]), isonitazene/protonitazene (n=30/73, [41%]), etonitazepyne (n=5/73, [7%]), etonitazene (n=3/73, [4%]), and etodesnitazene (n=2/73, [3%]). Nitazenes were detected in combination with the following noteworthy drugs: fentanyl (n=57/73, [78%]), benzodiazepine-type substances (n=56/73, [77%]), and/or xylazine (n=5/73, [7%]). Per survey data, 11 samples (15%) found to contain a nitazene opioid were associated with an overdose.

Conclusion: Nitazene opioids are highly potent and present a high risk of overdose and related adverse reactions when appearing unexpectedly and in combination with other noteworthy substances. Their novel identification in Toronto suggest that the city’s unregulated drug market remains highly dynamic, before and amidst the COVID-19 pandemic. Furthermore, these results suggest a trend towards higher-potency opioid analogues may be continuing. DCS is useful in raising awareness of drug composition and thereby contribute to overdose risk reduction and clinical response strategies.


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