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

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. Evaluate the association between daily buprenorphine adherence and illicit opioid use. 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). 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,  = .0002). 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.