Background: Opioid use disorder (OUD) is a major public health challenge. While effective treatment with opioid agonist therapy (OAT) exists, initiating and successfully completing induction remains difficult. Primary care is an ideal setting for OAT delivery, providing both an entry point into care and ongoing coordination with other services. The specific ways in which access, continuity of care, and comprehensiveness of primary care affect OAT induction success are not well understood.

Objective: To assess the causal association between primary care dimensions and first successful OAT induction among people diagnosed with OUD.

Methods: We conducted a population-based cohort study of patients first diagnosed with OUD in British Columbia, Canada (2014–2018). We used Fine and Gray’s proportional subdistribution hazards models to account for deaths. Inverse probability of treatment weighting was used to control for confounding. Analyses were also stratified by rurality.

Results: Among 17,184 patients, 34% achieved their first successful OAT induction, and 6% died during follow-up. Greater access to primary care was associated with a 24% increased likelihood of successful OAT induction (HR=1.24, 95% CI: 1.17-1.31). Continuity of care showed a weaker association (HR=0.96, 95% CI: 0.90-1.02). Comprehensiveness of primary care physicians was associated with a lower likelihood of successful OAT induction (HR=0.73, 95% CI: 0.67-0.81). Stratified analysis by setting showed that access to care is more crucial in rural areas (HR=1.47, 95% CI: 1.23-1.77) than in urban areas (HR = 1.25, 95% CI: 1.18-1.33).

Conclusions: Primary care dimensions influence successful OAT induction differently. Greater access facilitates successful induction, but higher comprehensiveness of care, which reflects the diversity of primary care physicians’ practice, may be associated with lower successful induction rates. More research is needed to understand how primary care impacts OUD patient outcomes.