Characteristics of fatal 'novel' benzodiazepine toxicity in Australia

The study aimed to determine: 1. The characteristics of all recorded cases of fatal drug poisoning involving 'novel' benzodiazepines (NBZDs) in Australia; 2. The toxicology of cases; and 3. The major autopsy findings.

Retrospective study of all deaths due to drug toxicity in Australia in which NBZDs were present in blood toxicology, retrieved from the National Coronial Information System (2000-2021). Information was collected on case characteristics, toxicology and major organ pathology.

A total of 40 cases were identified, the first occurring in 2015, with a median age of 26.5 years and 87.5% being male. Death was due to accidental toxicity in 92.5% of cases. There were extensive histories of substance use problems (80.0%) and mental health problems (32.5%). Etizolam was the most common NBZD (87.5%), followed by flubromazolam (15.0%), with other NBZDs detected in 20.0% (delorazepam, diclazepam, flualprazolam, flubromazepam, lormetazepam). Multiple NBZDs were present in 27.5%. Other drugs were present in 97.5%, most commonly opioids (70.0%), registered benzodiazepines (62.5%), psychostimulants (45.0%) and gabapentinoids (32.5%). A CNS depressant other than a NBZD was detected in 95.0% (n = 38). Autopsies were conducted and available for 30 cases, with pulmonary oedema (76.7%, n = 23), aspiration of vomitus (46.7%, n = 14) and acute bronchopneumonia (36.7%, n = 11) the most common diagnoses.

The 'typical' NBZD-related death was a young male who died due to accidental toxicity. Deaths most frequently involved etizolam and multiple substances, particularly depressants.