The Illicit Drug Reporting System (IDRS) has been conducted annually since 2000. The IDRS is a national drug monitoring system, designed to identify and track emerging trends of local and national concern in illicit drug use and markets. The IDRS forms part of the broader Drug Trends program.

This bulletin examines reported same-day use of drug classes that may carry particular risk when used in combination, and that make notable contributions to drug-related mortality in Australia.

Key findings

• One third or more of the sample (33-41%) reported same-day use of two drugs that increase risk for overdose.
• Pharmaceuticals, whether prescribed or non-prescribed, were involved in the majority of these combinations (23-33% of the sample).
• More than one quarter (26-46%) of those taking benzodiazepines or gabapentinoids daily did not report using them yesterday.

Discussion

Despite general declines in use of pharmaceuticals among successive IDRS cohorts, pharmaceuticals remain central in overdose deaths in Australia and are a key component of the risk profiles identified here. Among people reporting benzodiazepine use, around two thirds (69%) used some type of opioid on the same day (152 were estimated to have used benzodiazepines, 105 of these were estimated as using opioids on the same day), with similar patterns observed among people using gabapentinoids.

With counterfeit benzodiazepines often containing NPS from the benzodiazepine class, it is unlikely that any consumer will be able to reliably predict the duration of action, and several substances in this group have half-lives longer than 24 hours, making same-day use particularly high risk.

Our approach here to identifying use on the prior day, comparing reports of ‘daily use’ of a substance to what was recalled yesterday, highlights that habitual use of medications may be particularly prone to forgetting. The discrepancy between recalled use and previously reported daily use was low for drugs such as heroin, but much greater for benzodiazepines (>25% of those reporting daily use not reporting use yesterday) and gabapentinoids (>40%).

As such, it is important that harm-reduction messaging continues to emphasise the importance of avoiding same-day use of opioids (pharmaceutical or otherwise) with pharmaceuticals, whether they be prescribed or non-prescribed. Moreover, ensuring that naloxone is on hand (along with people around who are able to use it) continues to be a crucial message.

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Recommended citation

Bruno R, Radke S. Same-day use of risky substance combinations among a sample of people who frequently inject drugs in Australia, 2025. Drug Trends Bulletin Series. Sydney: National Drug and Alcohol Research Centre, UNSW Sydney; 2026. Available from: https://doi.org/10.26190/unsworks/32616

Funding and copyright

Drug Trends is supported by funding from the Australian Government Department of Health, Disability and Ageing under the Drug and Alcohol Program.

© NDARC, UNSW SYDNEY 2026 

This work is copyright. You may download, display, print and reproduce this material in unaltered form only (retaining this notice) for your personal, non-commercial use or use within your organisation. All other rights are reserved. Requests and enquiries concerning reproduction and rights should be addressed to the information manager, NDARC, UNSW Sydney, NSW 2052, Australia via drugtrends@unsw.edu.au.

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• Same-day use of risky substance combinations among a sample of people who frequently inject drugs in Australia, 2025

Contact

For further information, contact Raimondo Bruno at raimondo.bruno@utas.edu.au

Research areas