Suvorexant as an Adjunct to Buprenorphine in Persons Who Use Fentanyl

This study will enroll persons with opioid use disorder (N=120) who have recent fentanyl exposure (as assessed via urinalysis testing). Participants will be randomized to receive suvorexant or placebo for the duration of the study enrollment, which will serve as the between-groups experimental comparison. The study will consist of a brief (5 day) residential phase and 3-week outpatient phase. During the residential phase, all participants will be briefly maintained on a short acting opioid prior to induction onto sublingual (SL) buprenorphine (using either the buprenorphine or buprenorphine/naloxone product). At the end of the 5-day residential period, participants will be discharged to complete the \~3-week outpatient phase. During the outpatient period all participants will be maintained on SL buprenorphine/naloxone and continue to receive suvorexant or placebo, and at the end of the study participants will receive an injection of XR-buprenorphine (Sublocade). All buprenorphine procedures will be open label and will follow standard-of-care practices. Study medication during the outpatient period will be managed using an automated pill dispenser. Data collection will consist of forehead-based EEG monitoring, wrist-worn actigraphy/photoplethysmography, and questionnaires delivered during study visits or via cell-phone based ecological momentary assessments.