Intoxications in an Australian Emergency Department Involving 'Nitazene' Benzylbenzimidazole Synthetic Opioids (Etodesnitazene, Butonitazene and Protonitazene)

Benzimidazole synthetic opioids are highly potent mu-opioid receptor agonists with heroin-like effects, including dose-dependent respiratory depression and a high risk of abuse and toxicity. Benzimidazoles were first detected in 2019 in Europe and Canada, with analytical confirmation of etodesnitazene, protonitazene and butonitazene in 2021. We report the first detections of these compounds in Australia, in two patients presenting with drug toxicity to Emergency Departments (EDs) in the state of Victoria. Case 1 was a female in her 20s who rectally administered etodesnitazene and was found unconscious with respiratory depression and hypotension. Case 2 was a female in her 30s who presented to the ED in a sedated state after taking a formulation of protonitazene that also contained butonitazene, in addition to methylamphetamine. She responded positively to naloxone. Novel synthetic opioids were used with prior experience of the formulations purchased; however, the unpredictability of their effects was demonstrated by the acute toxicity experienced with this occasion of use. Toxicosurveillance of ED presentations with analytical confirmation of drugs is crucial in identifying emerging drugs in the community and informing harm reduction strategies.