Characteristics and time course of benzodiazepine-type new psychoactive substance detections in Australia: results from the Emerging Drugs Network of Australia - Victoria project 2020-2022

Introduction: The emergence of benzodiazepine-type new psychoactive substances (NPSs) are a growing international public health concern, with increasing detections in drug seizures and clinical and coronial casework. This study describes the patterns and nature of benzodiazepine-type NPS detections extracted from the Emerging Drugs Network of Australia - Victoria (EDNAV) project, to better characterise benzodiazepine-type NPS exposures within an Australian context. Methods: EDNAV is a state-wide illicit drug toxicosurveillance project collecting data from patients presenting to an emergency department with illicit drug-related toxicity. Patient blood samples were screened for illicit, pharmaceutical and NPSs utilising liquid chromatography-tandem mass spectrometry. Demographic, clinical, and analytical data was extracted from the centralised registry for cases with an analytical confirmation of a benzodiazepine-type NPS(s) between September 2020-August 2022. Results: A benzodiazepine-type NPS was detected in 16.5 % of the EDNAV cohort (n = 183/1112). Benzodiazepine-type NPS positive patients were predominately male (69.4 %, n = 127), with a median age of 24 (range 16-68) years. Twelve different benzodiazepine-type NPSs were detected over the two-year period, most commonly clonazolam (n = 82, 44.8 %), etizolam (n = 62, 33.9 %), clobromazolam (n = 43, 23.5 %), flualprazolam (n = 42, 23.0 %), and phenazepam (n = 31, 16.9 %). Two or more benzodiazepine-type NPSs were detected in 47.0 % of benzodiazepine-type NPS positive patients. No patient referenced the use of a benzodiazepine-type NPS by name or reported the possibility of heterogenous product content. Conclusion: Non-prescription benzodiazepine use may be an emerging concern in Australia, particularly amongst young males. The large variety of benzodiazepine-type NPS combinations suggest that consumers may not be aware of product heterogeneity upon purchase or use. Continued monitoring efforts are paramount to inform harm reduction opportunities.