Buprenorphine adherence and illicit opioid use among patients in treatment for opioid use disorder.

Background: Buprenorphine is a partial mu opioid agonist medication that has been shown to decrease non-prescribed opioid use, cravings, and opioid related morbidity and mortality. There is an assumption that full adherence is needed to achieve ideal treatment outcomes, and that non-adherence is associated with ongoing opioid use. However, literature documenting the strength of that assertion is lacking.Objectives: Evaluate the association between daily buprenorphine adherence and illicit opioid use.Methods: Secondary analysis of a 12-week randomized controlled trial of adults with opioid use disorder who recently initiated buprenorphine. Weekly study visits included self-report of daily buprenorphine adherence over the past 7 days (Timeline Follow Back method) and urine drug tests (UDT). A log-linear regression model accounting for clustering by participant was used to assess the association between buprenorphine adherence and illicit opioid use. Buprenorphine adherence was measured as a continuous variable (0-7 days).Results: Among 78 participants (56 men, 20 women, 2 nonbinary) with 737 visits, full 7-day adherence was reported at 70% of visits. The predominant form of non-adherence was missed doses (92% of cases). Each additional day of adherence was associated with an 8% higher rate of negative UDT for illicit opioids (RR = 1.08; 95% CI:1.03-1.13, p = .0002).Conclusion: In this sample of participants starting buprenorphine, missed doses were not uncommon. Fewer missed days was significantly associated with a lower risk of illicit opioid use. These findings suggest that efforts to minimize the number of missed days of buprenorphine are beneficial for treatment outcomes.