Fig. 2

Treatment retention, abstinence, and plasma buprenorphine concentrations in opioid-injecting participants. Participants included in the analysis were those who received at least one maintenance dose of BUP-XR (300 mg or 100 mg); this corresponds to randomized participants after excluding: participants from site 020, placebo arm, participants who only had their first and/or second BUP-XR injections, and one participant who missed information on the route of opioid use (i.e., injectable vs. non-injectable). A The treatment retention rate following the first maintenance dose was estimated using the Kaplan–Meier method with risk adjustment via propensity score IPW. Treatment retention rate: Time to study discontinuation was defined as the number of days from the first maintenance dose until the last scheduled visit for opioid assessment observed in the study. Participants who did not discontinue the study were censored at the last opioid assessment visit. B Risk-adjusted comparison of the proportion of abstinent participants (as observed) by visit via propensity score IPW. Participants who did not provide both UDS and negative self-report at a specific visit were excluded from the percentage denominator for that visit, and participants who had missing value for either UDS or negative self-report (but not both) were considered as positive for that visit and included in the denominator. C Mean buprenorphine plasma concentration–time profiles for the two BUP-XR dose groups. IPW inverse propensity weighting; N Pseudo-number of participants in the analysis after re-weighting via inverse propensity weighting for risk adjustment, SD standard deviation, UDS urine drug screen. Week 0 (Screening visit), Week 1 (baseline; opioid use was assessed before the first BUP-XR administered at that visit), Week 9 (the visit when the first maintenance dose was administered)