Neurofunctional phenotyping to investigate the role of the orexin system at the intersection of opioid use disorder and insomnia: a protocol for a randomised, placebo-controlled clinical trial of lemborexant in patients with insomnia receiving buprenorphine.

introductionInsomnia is a common complaint among patients with opioid use disorder (OUD) maintained on buprenorphine (BUP). However, people with OUD have historically been excluded from insomnia clinical trials, leaving clinicians without evidence-based treatment options for this patient population. Lemborexant, the Food and Drug Administration (FDA)-approved dual orexin receptor antagonist for the treatment of insomnia, was recently shown to be safe and tolerable among a sample of patients with insomnia who were maintained on BUP. We hypothesise that pharmacologically antagonising the orexin system with lemborexant may improve insomnia symptoms in individuals with OUD and also enhance BUP treatment benefits by improving performance in neurofunctional domains identified in the National Institute on Drug Abuse Phenotyping Assessment Battery. METHODS AND ANALYSIS: Participants with insomnia and OUD who have been stabilised on BUP for at least 4 weeks will be randomly assigned to receive either lemborexant (n=50) or placebo (n=50) for 8 weeks. Participants will complete assessments at baseline, during the 8-week intervention, postintervention and at a 2-week follow-up. Primary outcomes are insomnia severity and impulsivity. Secondary measures include objective sleep metrics (total sleep time, sleep efficiency, sleep onset latency and wake after sleep onset) and performance in the neurofunctional domains of negative emotionality and metacognition. ETHICS AND DISSEMINATION: The study was approved by the Virginia Commonwealth University Institutional Review Board in April 2025 (protocol number HM20031777). Data collection began in May 2025 and is expected to be completed by May 2029. The trial is conducted under FDA IND no. 154797 (FGM). The dissemination plan for the trial includes presentations at local and national conferences, submission of primary and secondary outcome manuscripts for publication in peer-reviewed journals and circulation of findings to popular media outlets, as available. Results will also be shared with interested participants and clinical collaborators upon completion of the trial. TRIAL REGISTRATION NUMBER: NCT06981195.