Admissions to publicly-funded residential treatment for opioid use disorder and opioid toxicity outcomes after discharge in Ontario, Canada: A population-based repeated cross-sectional study

With Canadian provinces expanding investments for bed-based inpatient (i.e., residential) substance use treatment, it’s important to understand who accesses these programs and their treatment outcomes. Therefore, the aim of our study was to describe admissions to publicly-funded residential treatment for opioid use disorder (OUD) and opioid toxicities rates following discharge. We conducted a population-based repeated cross-sectional study of publicly-funded residential treatment for OUD in Ontario, Canada, between July 1, 2013 and June 30, 2022. We calculated population-adjusted residential treatment admission rates and used joinpoint regression models to assess significant changes in monthly percent changes (MPC). We reported characteristics of discharged clients and weekly rates of fatal or non-fatal opioid toxicity 1-year post-discharge. Among the first identified residential treatment episode for each client, we determined the proportion who had an opioid toxicity event within 28-days post-discharge, overall and stratified by admission date, age, sex, mandated treatment, and discharge reason. Over the study period, admissions fluctuated monthly (from 1.5 [N = 18] to 11.9 [N = 136] per 1,000,000), declining gradually until December 2019 (MPC: -0.3%; p-value = 0.0009) before dropping abruptly between January and April 2020 (MPC: -20.3%; p-value = 0.44) and then rising soon thereafter (MPC, 2.5%; p-value = 0.0001). Overall, 60.8% of clients (N = 9,388; mean age, 33.1 + 10.2 years; 64.1% male) completed their treatment program. Within 28 days post-discharge, 1.4% experienced an opioid toxicity, with higher rates among clients who were male (1.7%), mandated to treatment (2.1%), and discharged early, both voluntarily (2.0%) and involuntarily (2.8%). Despite rising investments into residential treatment programs, our findings showed admissions for OUD dropped substantially early in the COVID-19 pandemic and remained below pre-pandemic levels in the subsequent two years. Importantly, high rates of early discharge and opioid toxicity soon thereafter underscore the need to implement quality standards for residential treatment programs in Ontario and throughout Canada.