Joshua Bird is a Doctoral Candidate in Population & Public Health at the University of British Columbia. His research interests lie at the nexus of epidemiology, data science and public health policy, with particular emphasis on quasi-experimental and observational study designs. Currently, his work is focused on leveraging quantitative methods and population-level administrative health databases to examine how changes in the unregulated drug supply impact health and healthcare utilisation outcomes over time. Prior to re-entering academia he was a civil servant, working most recently as a Statistician in the Population Health Directorate at the Scottish Government.

Abstract

Impact of drug scheduling on detection of bromazolam in the unregulated opioid supply: An interrupted time series analysis

Aims: Adulteration of the unregulated opioid supply with benzodiazepines such as bromazolam is a significant public health concern due to additive effects on respiratory depression and overdose risk. National and international bodies maintain drug schedules aimed at regulating novel psychoactive substances based on their risk and harm potential, yet little is known about how scheduling impacts the unregulated drug supply.

Methods: We derived data from 43,760 samples tested at 101 community drug checking sites in British Columbia between March 2022 and February 2026. Using interrupted time series, we assessed changes in bromazolam detection in opioids following three interventions: when bromazolam scheduling was recommended per the United Nations Commission on Narcotic Drugs; when the People’s Republic of China banned bromazolam; and when United Nations Commission on Narcotic Drugs scheduling enforcement began.

Results: Bromazolam emerged in March 2022, peaked at 9% in June 2023, and fell to 0.5% in November 2025. In interrupted time-series analyses, the United Nations Commission on Narcotic Drugs recommendation was associated with significant slope decreases (-0.41 percentage points[pp]; 95%CI: -0.60,-0.26), and People’s Republic of China’s ban with significant step increases (2.98pp; 95%CI: 0.95,5.02) in bromazolam detection. Following United Nations Commission on Narcotic Drugs enforcement, the absolute trend stabilised at a lower level compared to the pre-scheduled period.

Conclusions: Bromazolam scheduling recommendations coincided with observable changes in the contents of expected opioid samples. This suggests that unregulated drug manufacturers may be responsive to proposed and actual scheduling by pivoting to unscheduled alternatives. Drug scheduling as a supply-side intervention must be considered alongside wider harm reduction measures aimed at mitigating public health risks posed by an increasingly unstable unregulated drug supply.