Changes in the use of non-prescribed hydromorphone and unregulated opioids use in Vancouver, Canada, 2018-2022

Background: In March 2020, following the emergence of the COVID-19 pandemic, the Canadian province of British Columbia initiated novel programs involving the prescribing of pharmaceutical opioids (primarily hydromorphone) as alternatives to opioids from the unregulated supply (e.g., fentanyl). We estimated potential changes in the use of non-prescribed hydromorphone and unregulated opioids pre- vs. post-pandemic emergence among people who use drugs (PWUD) in Vancouver, British Columbia. 
 
Methods: Data were derived from two cohorts of community-recruited PWUD in Vancouver in 2018-2022. We employed an interrupted time series analysis to estimate the combined effects of the pandemic and hydromorphone prescription programs on the monthly prevalence of non-prescribed hydromorphone and unregulated opioids use. Multivariable generalized estimating equations model was used to determine factors associated with non-prescribed hydromorphone use in 2020-2022.
 
Results: Among 1,164 PWUD, there was a significant immediate increase post-pandemic emergence in non-prescribed hydromorphone use (+4.4%; 95% confidence interval [CI]: 1.5%, 7.3%) and a significant immediate decrease in unregulated opioids use (-4.5%; 95% CI: -7.2%, -1.8%) but no significant changes in the monthly trends. In the multivariable analysis, ³daily use of unregulated stimulants (adjusted odds ratio [AOR]=1.85; 95% CI: 1.28-2.66), chronic pain (AOR=1.50; 95% CI: 1.04-2.14) and being prescribed hydromorphone as pharmaceutical alternatives (AOR=1.58; 95% CI: 1.02-2.45) were associated with non-prescribed hydromorphone use.
 
Conclusions: We found significant and immediate increases in non-prescribed hydromorphone use post-pandemic emergence, which coincided with significant decreases in unregulated opioids use. Non-prescribed hydromorphone might have served multiple purposes in this setting, including as a pharmaceutical alternative to unregulated opioids.