A Quantitative Analysis of Street‐Level Drugs Seized in New South Wales, Australia: Purity, Dose and Adulterants

ABSTRACT Introduction The Combined Surveillance and Monitoring of Seized Samples (CoSMoSS) program is a joint harm reduction initiative between NSW Health and NSW Police Force. Here, we examine the contents and purity of a sample of seized suspected target drugs (cocaine, heroin, methamphetamine and 3,4‐methylenedioxymethamphetamine ‘MDMA’). Methods Between January 2021 and March 2025, 3378 street drug samples seized during routine operations by NSW Police Force within music festivals or specified geographic regions and suspected by police to contain a target drug were selected for expedited quantitative analysis with GC–MS, with results available within 1 month. Results As expected, most samples contained at least one target drug. About 1 in 6 samples (16.5%) were found to contain at least one adulterant and 3.9% of samples contained a novel psychoactive substance, including dipentylone, nitazenes, fentanyl analogues and novel benzodiazepines. Purity information is presented; median MDMA tablet dose was 104 mg and capsule dose was 64 mg (free base) and was higher in more recent years. Discussion and Conclusions Some rarer substances with higher or unknown risk potential, including novel psychoactive substance, were detected. Adulteration of cocaine and methamphetamine with opioids and high variability in MDMA purity and dose, remain public health issues. CoSMoSS helps inform harm reduction messaging. Analysis of seized substances provides high‐quality objective information about illicit drug contents and purity, enabling dissemination to the community when high risk substances are identified. These findings can also inform harm reduction messaging and programs and are monitored within the NSW Health drug early warning system.