Investigating drug trends among people who inject drugs: Temporal, geographical and operational analyses of used syringes in Sydney, Australia

Background

Understanding drug use among people who inject drugs (PWID) is frequently based on self-reported data. Whilst insightful, it can be subjective and provides limited information on the drug composition. The chemical analysis of the residual drug content in used syringes has been shown to complement self-reported information. Chemical analysis can confirm the main drug injected and detect other components, such as adulterants. Drug use is dynamic; hence temporal, geographical and operational analyses might provide greater insight into market behaviours and the consumption trends of PWID.

Objectives

This study aims to examine the residual drug content of used syringes over time and space to observe trends in injecting drug use. Operational sampling was also investigated as a tool to characterise emerging health crises through targeted implementations.

Methods

Used syringes (n = 2148) were collected through multiple periods (2022 – 2024) across different locations in metropolitan and Western Sydney, including the Uniting Medically Supervised Injecting Centre (MSIC). The residual drug content was extracted from the used syringes before detection via gas chromatography–mass spectrometry (GC–MS) and ultra-performance liquid chromatography – tandem mass spectrometry (UPLC-MS/MS). The syringes collected from MSIC were compared to the drugs self-reported by MSIC clients.

Results

Within all samples, heroin and methamphetamine were the most frequently injected drugs, followed by pharmaceutical opioids. Temporal drug trends remained relatively static, whereas distinct sub-populations of PWID emerged from geographical analyses. Polydrug and adulterant analysis identified the presence of a diverse range of drugs within syringes, including some drugs of concern, such as fentanyl within heroin syringes. Operational sampling identified protonitazene as the likely cause of an emerging overdose cluster.

Implications

This research aligns well with Australia's harm minimisation approach to drugs and has broader implications for harm minimisation globally. It holds great potential for harm reduction at an individual level for PWID by providing insights into the current drug market. Targeted applications of syringe analysis may be the only tool to gather information on drug use among PWID when traditional data sources are unavailable. Hence, broader implementations at the national level might capture unique insights into injecting drug consumption trends.