BACKGROUND AND AIMS: In British Columbia, Canada, an initiative was implemented in 2020 to reduce overdose mortality by prescribing pharmaceutical opioids (primarily hydromorphone) as a substitute for the toxic unregulated drug supply. This study estimated changes in the level and trend of unregulated opioid use and non-prescribed hydromorphone use before and after the implementation of prescribed pharmaceutical alternatives (PPA) among a cohort of young people who use drugs.

DESIGN: Longitudinal observational study. Data were drawn from a community-recruited prospective cohort study. We used interrupted time series (ITS) analyses to assess level and trend of self-reported quarterly unregulated opioid and non-prescribed hydromorphone use before, upon and after the implementation of PPA. We used generalized estimating equations (GEE) models to adjust for factors known to influence substance use.

SETTING: Vancouver, British Columbia, Canada, between December 2015 and May 2024.

PARTICIPANTS: 644 street-involved young people who use drugs (median age at baseline: 23.4 years; 32.6% women).

MEASUREMENTS: The main outcomes were self-reported any unregulated opioid use and any non-prescribed hydromorphone use in the past six months, obtained through interviewer-administered questionnaires. The primary explanatory variables for the GEE analyses were: time in quarters, interview date after PPA implementation and an interaction term between time and PPA implementation.

FINDINGS: 436 (67.7%) participants reported unregulated opioid use, and 124 (19.3%) reported non-prescribed hydromorphone use during the study. In the ITS analysis, unregulated opioid use showed a statistically significant immediate drop following PPA implementation [per-quarter coefficient (PQC): -5.30; 95% confidence interval (CI) = -10.51 to -0.09], with no statistically significant trend observed in the post-PPA period (PQC: 0.06; 95% CI = -0.35 to 0.47). For non-prescribed hydromorphone use, a downward trend was observed in the pre-PPA period (PQC: -0.46; 95% CI = -0.80 to -0.12). Following PPA implementation, no level change was observed (PQC: 2.61; 95% CI = -2.60 to 7.82), and the pre-existing downward trend was halted (PQC: 0.31; 95% CI = -0.10 to 0.72). The GEE analysis confirmed these opposing trends.

CONCLUSIONS: British Columbia, Canada's 2020 implementation of prescribed pharmaceutical alternatives to reduce opioid overdose mortality was associated with a statistically significant decline in unregulated opioid use and a halt to the pre-existing downward trend in non-prescribed hydromorphone use among a cohort of young people.