Increased distance was associated with lower daily attendance to an opioid treatment program in Spokane County Washington

Objective: Adherence to opioid agonist therapy with methadone is associated with improved clinical and community outcomes such as reductions in drug use, criminal behavior, high-risk sexual behavior, and mortality. However, the need for daily attendance for witnessed ingestion may comprise adherence. Methods: Data for this study were obtained from the Spokane Regional Health District's Treatment Services database. Generalized linear models with negative binomial log link function were used to assess the association between distance to the only state-funded opioid treatment program (OTP) in Spokane County, Washington and the number of missed methadone doses in the first month of treatment. Results: In total, 892 individuals received methadone treatment at this OTP between February 2015 and December 2017. In the adjusted multivariable model, clients who lived more than 10 miles from the OTP were more likely to miss doses compared to individuals who lived within 5 miles of the clinic (IRR = 1.29, 95%CI = 1.03-1.61, p = 0.03). Clients who lived less than 5 miles and between 5 and 10 miles from the OTP were equally likely to miss treatment doses (IRR = 1.02, 95%CI = 0.84-1.23, p = 0.86). Conclusions: This study found significant positive associations between distance to an OTP and the number of missed doses in the first month of treatment. Findings suggest the need to improve the spatial availability of OTPs to optimize opioid use disorder treatment outcomes.