Consumption of psychotropic drugs is a major economic and public health challenge in Australia. Wastewater-based epidemiology (WBE) and drug checking have emerged as complementary tools to monitor this market. WBE estimates drug use within communities for target compounds and their metabolites, while drug checking is a free service available in some Australian jurisdictions, which allows individuals to verify drug purity and composition. In this work, wastewater samples were collected from five sites across Queensland (n = 3), New South Wales (n = 1) and Victoria (n = 1) over the 2024-25 New Year holidays, while drug checking was carried out at a site in central Canberra over December-January. Wastewater samples were analysed for alcohol, illicit drugs and new psychoactive substances (NPS) using liquid chromatography-tandem mass spectrometry. Methamphetamine was the most consumed illicit substance across all sites, while cocaine and MDMA showed distinct increases over the New Year period. Among NPS, bromazolam and 2'-fluoro-2-oxo-PCE were most prevalent, while ketamine was consistently detected at regional sites with consumption 2.8-3-fold higher on New Year's days. Drug checking revealed prevalence of MDMA, cocaine and ketamine. NPS were detected in 15%-20% of total drug samples submitted, with N,N-dimethylpentylone and 2'-fluoro-2-oxo-PCE the most frequently found. This study is the first to demonstrate the potential synergy between WBE and drug checking, highlighting how their complementary roles can enhance drug surveillance, early warnings for emerging psychoactive substances and monitoring of changes in drug consumption during high-risk periods.
