Efficacy analyses
OI, psychiatric
DISORDER
Urine drug screens (UDS) and self-reports for opioid use were collected weekly; abstinence at a given week was defined as opioid-negative UDS combined with negative self-reports for opioids (Timeline Followback interviews) [Variables measured before randomization: age, gender, race (black vs. non-black), body mass index, years of opioid use, current alcohol use, current tobacco use, cocaine use (self-reported history or UDS positive at screening), polydrug use (self-reported history or UDS positive at screening), psychiatric disorder, daily opioid use in the past 30 days prior to screening, and last sublingual buprenorphine dose (mg) before the first BUP-XR injection.Variables measured post-randomization and prior to the first maintenance dose on week 9: participant’s percentage cocaine abstinence during weeks 1–9 (combined UDS and self-reports); the most recent results for Clinical Opiate Withdrawal Scale (COWS) [Each participant’s percentage abstinence was calculated after the first (weeks 10–25), second (weeks 14–25), and third (weeks 18–25) maintenance doses as the proportion (%) of negative opioid use results among the corresponding 16, 12, and 8 weekly assessments, respectively. Missing UDS or self-report at a specific visit (or both as a result of study discontinuation) were treated as positive for opioid use for that week (Table 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). Treatment retention rate following the first maintenance dose was estimated for the OI using the Kaplan–Meier method with risk adjustment via propensity score IPW. Time to treatment 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 completed the study were censored at their last opioid assessment visit.