A retrospective cohort study

Background
First Nations People are disproportionately impacted by the opioid toxicity crisis in Canada. While many First Nation communities have expanded access to treatment, there is a need to better understand the factors associated with early discontinuation of opioid agonist therapies (OAT).

Objective
We investigated factors associated with OAT retention within the first year of treatment among First Nations People in Ontario, Canada.

Methods
We conducted a population-based retrospective cohort study including all registered (Status) First Nations People aged 15 years or older initiating OAT between January 2013 and March 2021. 

Results
We identified 9,074 new episodes of buprenorphine/naloxone and 8,806 new episodes of methadone. The median age at initiation was 31, and 50.1% were females. Median time to treatment discontinuation was shorter among buprenorphine/naloxone episodes (42 days) compared to methadone (71 days). Several factors were associated with buprenorphine/naloxone and methadone retention, including living in moderately-sized urban areas and being recently dispensed non-OAT opioids. Factors associated with higher rates of discontinuation included recent opioid toxicities and recent methadone treatment. Methadone discontinuation increased over time; however this pattern was not observed for buprenorphine/naloxone.

Conclusion
In this cohort study among First Nations People, we found low rates of OAT retention. Although retention was higher for methadone, it declined over time. This highlights important gaps in OAT provision for First Nations People which may be improved by investments into First Nations-led treatment programs that integrate traditional, land-based programs to better support people with OUD across the province.

Date Released: June 30, 2025