Suvorexant as an Adjunct to Buprenorphine in Persons Who Use Fentanyl

This is a 4-week, randomized-controlled trial of suvorexant vs placebo in persons with opioid use disorder who have recent fentanyl exposure. Participants will first undergo a 5-day residential phase wherein participants are stabilized on sublingual buprenorphine/naloxone, followed by a 3-week outpatient phase wherein participants are maintained on sublingual buprenorphine/naloxone and transitioned to extended-release buprenorphine).

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.

Eligibility Criteria:
Inclusion Criteria:

* Aged 18-65
* Meets DSM-5 criteria for opioid use disorder (OUD) with evidence of physical dependence on opioids
* Provides a urine sample that tests positive for fentanyl and/or fentanyl analogues
* Interest in being maintained on buprenorphine for OUD
* Plans to reside in current area for study period
* Achieving a study maintenance dose of \&gt;=8mg sublingual buprenorphine/naloxone
* Willing to comply with study protocol
* Have no clinically significant chronic medical or surgical disorders or conditions that are judged by the investigators to prevent participation

Exclusion Criteria:

* Medically contraindicated for buprenorphine, extended-release (XR)-buprenorphine (Sublocade), or suvorexant (as per medication labels)
* Pregnant or breast feeding
* Severe Diagnostic and Statistical Manual (DSM)-5 alcohol or benzodiazepine use disorder or evidence of alcohol/benzodiazepine physical dependence
* Have a known allergy to the study medications
* Past 30-day prescribed use of suvorexant for the indication of insomnia
* Current benzodiazepine or other prescribed medication for the indication of insomnia
* Urine sample testing positive for benzodiazepine at screening and admission to residential treatment
* Current narcolepsy, restless leg syndrome or sleep paralysis
* High risk for current sleep apnea
* Current (past 30-day) suicidal behaviors
* Severe hepatic or renal impairment

  * aspartate aminotransferase (AST) or alanine aminotransferase (ALT) \&gt;3x upper limit of normal (ULN)
  * Total bilirubin \&gt;2x ULN
  * Creatinine \&gt;1.5x ULN
* Past year clinically-significant psychiatric condition judged to interfere with study participation
* Lack of access to stable housing (necessary for electronic pill dispenser charging)
* Have circumstances that would interfere with study participation (e.g., impending jail)