Extended-release pharmacotherapy for opioid use disorder (EXPO): protocol for an open-label randomised controlled trial of the effectiveness and cost-effectiveness of injectable buprenorphine versus sublingual tablet buprenorphine and oral liquid methadone

Background: Sublingual tablet buprenorphine (BUP-SL) and oral liquid methadone (MET) are the daily, standard-of-care (SOC) opioid agonist treatment medications for opioid use disorder (OUD). A sizable proportion of the OUD treatment population is not exposed to sufficient treatment to attain the desired clinical benefit. Two promising therapeutic technologies address this deficit: long-acting injectable buprenorphine and personalised psychosocial interventions (PSI). This study will determine (A) the effectiveness and cost-effectiveness - monthly injectable, extended-release (BUP-XR) in a head-to-head comparison with BUP-SL and MET, and (B) the effectiveness of BUP-XR with adjunctive PSI versus BUP-SL and MET with PSI. Safety, retention, craving, substance use, quality-adjusted life years, social functioning, and subjective recovery from OUD will be also evaluated.

Methods: This is a pragmatic, multi-centre, open-label, parallel-group, superiority RCT, with a qualitative (mixed-methods) evaluation. The study population is adults. The setting is five National Health Service community treatment centres in England and Scotland. At each centre, participants will be randomly allocated (1:1) to BUP-XR or SOC. At the London study co-ordinating centre, there will also be allocation of participants to BUP-XR with PSI or SOC with PSI. With 24 weeks of study treatment, the primary outcome is days of abstinence from non-medical opioids during study weeks 2-24 combined with up to 12 urine drug screen tests for opioids. For 90% power (alpha, 5%; 15% inflation for attrition), 304 participants are needed for the BUP-XR versus SOC comparison. With the same planning parameters, 300 participants are needed for the BUP-XR and PSI versus SOC and PSI comparison. Statistical and health economic analysis plans will be published before data-lock on the Open Science Framework. Findings will be reported in accordance with the Consolidated Standards of Reporting Trials and Consolidated Health Economic Evaluation Reporting Standards.

Discussion: This pragmatic randomised controlled trial is the first evaluation of injectable BUP-XR versus the SOC medications BUP-SL and MET, with personalised PSI. If there is evidence for the superiority of BUP-XR over SOC medication, study findings will have substantial implications for OUD clinical practice and treatment policy in the UK and elsewhere.

Trial registration: EU Clinical Trials register 2018-004460-63.