Opioid-related emergency department visits and deaths after a harm-reduction intervention: a retrospective observational cohort time series analysis.

Background: To date, there has been little research on the effect of safe consumption site and community-based naloxone programs on regional opioid-related emergency department visits and deaths. We sought to determine the impact of these interventions on regional opioid-related emergency department visit and death rates in the province of Alberta.

Methods: We used a retrospective observational design, via interrupted time series analysis, to assess municipal opioid-related emergency department visit volume and opioid-related deaths (defined by poisoning and opioid use disorder). We compared rates before and after program implementation in individual Alberta municipalities and province-wide after safe consumption site (March 2018 to October 2018) and community-based naloxone (January 2016) program implementation.

Results: A total of 24 107 emergency department visits and 2413 deaths were included in the study. After safe consumption site opening, we saw decreased opioid-related emergency department visits in Calgary (level change -22.7 [-20%] visits per month, 95% confidence interval [CI] -29.7 to -15.8) and Lethbridge (level change -8.8 [-50%] visits per month, 95% CI -11.7 to -5.9), and decreased deaths in Edmonton (level change -5.9 [-55%] deaths per month, 95% CI -8.9 to -2.9). We observed increased emergency department visits after community-based naloxone program implementation in urban Alberta (level change 38.9 [46%] visits, 95% CI 33.3 to 44.4). We also observed an increase in urban opioid-related deaths (level change 9.1 [40%] deaths, 95% CI 6.7 to 11.5).

Interpretation: The results of this study suggest differences exist between municipalities employing similar interventions. Our results also suggest contextual variation; for example, illicit drug supply toxicity may modify the ability of a community-based naloxone program to prevent opioid overdose without a thorough public health response.