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 the percentage of participants who combined two or more drugs in the same syringe in the month prior to interview, how many times the drugs were combined in the same syringe, the specific drugs combined and sociodemographic and health factors associated with participants who reported combining two or more drugs in the same syringe.

Key findings

• Among the national IDRS sample (n=865), 18% of participants reported combining two or more drugs in the same syringe in the month preceding interview.
• The majority had done so on multiple occasions, with the most common combination, on the last occasion of combining two or more drugs, being methamphetamine crystal and heroin (59.2%).
• Among those who reported combining two or more drugs in the same syringe in the month prior to interview and responded (n=147), the majority (84%) reported combining two drugs in the one syringe, and 13% reported combining three drugs.
• Factors associated with combining two or more drugs in the same syringe in the month preceding the interview in 2025 were: being male, daily injection, using drugs for 24 hours or more without sleep, and needle sharing.

Discussion

Almost one fifth of the 2025 IDRS sample reported combining two or more drugs in the same syringe in the month preceding interview, with methamphetamine crystal and heroin the most common combination of drugs used on the most recent occasion. This is not surprising given that opioids and stimulants are the two most commonly injected drug classes among people who inject drugs in Australia, and is broadly similar to what was reported in 2017-2019 data from the Melbourne Injecting Drug User Cohort Study, in which approximately one third reported co-injecting drugs in the past month, and 54% of this subsample injecting a combination of methamphetamine and heroin. Further, a study in Seattle, Washington found that co-injection of methamphetamine and opioids had doubled between 2017 and 2019, while analysis of syringe residue across various sites in Sydney found that the second most frequent mixture was heroin and methamphetamine (alongside other compounds such as morphine, codeine, methadone and caffeine), although it is unknown whether this was the result of concurrent use or reuse of needles. These findings are of concern given the significant strain that the combined use of opioids and stimulants can place on both the cardiovascular and respiratory systems.

While earlier studies have linked co-injection of methamphetamine and opioids with poorer physical and mental health outcomes and an elevated risk of overdose and mortality, our findings showed no association with either mental health or overdose. However, our findings identified that gender, daily injecting and needle sharing were significantly associated with higher odds of co-injection, consistent with existing research, and suggest that harm reduction initiatives tailored to this behaviour may be particularly important for individuals with higher risk injecting and drug use patterns.

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Recommended citation

Karlsson A, Peacock A & Sutherland R. Combination of two or more drugs in the same syringe among a national sample of people who regularly inject drugs in Australia, 2025. Drug Trends Bulletin Series. Sydney: National Drug and Alcohol Research Centre, UNSW Sydney; 2026. Available from: doi.org/10.26190/unsworks/31939

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 

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• Combination of two or more drugs in the same syringe among a national sample of people who regularly inject drugs in Australia, 2025

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