designed to mimic brand-name drugs like Valium and Xanax but with greater potency – have spiked in the last six years.
Out of nearly 260 fatal NBZD-related toxicity cases reported since 2013, about 87% of these deaths occurred between 2020 and 2025, according to findings from the National Drug and Alcohol Research Centre, UNSW Sydney.
Emeritus Professor Shane Darke, who led the study, said the rapid increase in fatal overdoses from the unregulated drugs was a major clinical and public health concern.
"People who use novel benzodiazepines need to be aware that there is no safe way to use these drugs, and that death can – and does – occur," Professor Darke said.
"Compared to legal benzodiazepines, such as diazepam (Valium) and alprazolam (Xanax), the illicit versions produce stronger sedation and more severe respiratory depression, especially when combined with other substances."
What did the research show?
As part of the study, published in Drug and Alcohol Dependence, the authors examined all NBZD-related poisoning deaths recorded in the national coronial database since 2000.
A total of 258 cases were identified – the first in 2013 – and the vast majority (225 cases) occurred from 2020 onwards.
There were 15 different NBZDs detected, the most frequent of which were etizolam (48%), bromazolam (38%), flualprazolam (12%), and clonazolam/8-aminoclonazolam (11%).
Cases in the 2020s were more than four times more likely to have multiple NBZBs detected in blood toxicology results, which could partially explain the increase in deaths.
But the authors said the true extent of NBZB-related deaths was likely to be higher, due to limitations in testing, lags in data availability and the emergence of newer compounds.
In addition to harm reduction services such as drug checking, Professor Darke stressed the need for improved awareness of the signs of overdose that require medical attention.
"In two-thirds of the fatal overdoses we analysed, other people were in the immediate vicinity and could have been able to render prompt assistance if they were aware that an overdose was occurring," Professor Darke said.
"Yet only in half of these instances, assistance was provided."
Professor Darke also called for toxicology screening for NBZDs in emergency departments to be expanded in all jurisdictions to get a clearer picture of the extent of harms from their use.
The next step?
Dr Jack Freestone, a Postdoctoral Research Fellow at the National Centre for Clinical Research on Emerging Drugs, said the spike in NBZD-related deaths reflected growing use of the drugs as seen in surveys, hospitalisations data, and drug alerts.
"There were 23 novel benzodiazepine-related alerts issued by health authorities between 2020 and July 2025, with nearly half of these being issued in 2025 alone," said Dr Freestone, who has separately reported on the issue (most recently in Drug and Alcohol Review).
"They are also the most frequently detected type of novel psychoactive substances in Australian emergency department admissions."
To develop more effective health interventions, including harm reduction and support for dependence and withdrawal, Dr Freestone said the behaviours and characteristics of people using the drugs needed to be better understood.
"That is why we've launched the Navigating Novel Benzos Study – to learn about people's experiences and the strategies they use to look after themselves, source the drugs and reduce harm," Dr Freestone said.
"This will be highly valuable for reducing the harms associated with novel benzodiazepines and improve our knowledge of the rapidly evolving nature of these compounds."
