INTRODUCTION: Clonazolam is an unregistered novel benzodiazepine which emerged in global illicit drug markets in 2014. We describe the clinical features of four cases of non-fatal clonazolam mono-intoxications from patients presenting to emergency departments in Australia.

CASES: Four patients aged between 16 and 19 years presented to hospital with a sedative toxidrome (Glasgow Coma Scale range 8-13) and elevated heart rate (median heart rate 100 beats per minute, range 92-105) following reported benzodiazepine exposure. Three patients reported the use of a large quantity (7-20 tablets) of Xanax, a brand of alprazolam not commercially available in Australia. Two patients required nasopharyngeal airway insertion following the development of airway obstruction. The median time to return of a normal conscious state (Glasgow Coma Scale 15) was 23 h (range 5-30 h). Clonazolam (range 0.2-2.1 µg/L) and its main metabolite 8-aminoclonazolam (range 5.9-19.1 µg/L) were the only substances detected by liquid chromatography-tandem mass spectrometry in blood samples of all patients.

CONCLUSION: Clonazolam intoxication resulted in sedation with mild sinus tachycardia. Three patients who reported multiple tablet exposures experienced prolonged sedation, and two of these patients developed airway obstruction. In this series, clonazolam was unknowingly ingested through possible illicit substitution within an unregulated counterfeit benzodiazepine product.