Evaluation of a peer recovery support program adapted to target retention in clinic-based medication for opioid use disorder treatment - PROJECT ABSTRACT Drug overdoses are at record levels in the US, driven primarily by the ongoing opioid use disorder (OUD) epidemic. Medications for opioid use disorder (MOUD) have been shown to safely and effectively treat OUD, reduce overdose and overdose death, and facilitate long-term recovery. However, retention in MOUD treatment often falls short of the 6-12-month duration necessary for sustained recovery, and early termination from MOUD is a risk factor for overdose. Peer recovery support (PRS; i.e., support services provided by trained “peers” with lived experience of addiction and recovery) holds substantial promise as a strategy for improving retention in MOUD, yet virtually no rigorous research has been conducted on its effectiveness in this setting. The overarching aim of the proposed project is to engage stakeholders to adapt PRS specifically for use in outpatient MOUD settings and evaluate the effectiveness of the PRS program in improving patient retention across multiple geographically diverse MOUD clinics. The Practical, Robust Implementation and Sustainability Model (PRISM), a contextually expanded version of the Reach, Adoption, Effectiveness, Implementation, and Maintenance (RE- AIM) framework will be used across the two phases of the project to ensure that the resulting PRS program and study findings can be translated directly into practice. In the R61 phase, we propose a Community-Based Participatory Research approach to adapting PRS services for outpatient MOUD treatment settings. We will assemble and collaborate with two community boards throughout the R61 and R33 phases to co-develop all aspects of the PRS program, training and supervision plan for peer recovery specialists, and elements of the subsequent clinical trial. Community boards will include: 1) patients with lived experience with MOUD treatment; and 2) MOUD providers/staff/administers, peer recovery specialists, and payors. Next, we will conduct a mixed- methods pilot evaluation to test feasibility and make refinements to the PRS program, peer training and supervision plan, and trial methods. In the R33 phase, we will conduct a randomized controlled trial comparing standard outpatient MOUD care (SC) versus SC plus the adapted PRS program (SC+PRS). The primary outcomes are treatment retention and length of time in treatment at 6 months; secondary outcomes include 12- month retention, illicit opioid use, and patient satisfaction with meeting treatment goals. Exploratory analyses will examine potential moderators (e.g., rurality, addiction severity) and mediators (e.g., recovery capital, internalized stigma) of the effect of SC+PRS, including how the degree of engagement with PRS impacts effectiveness. Finally, this project will evaluate facilitators and barriers to PRS program delivery and sustainability using a mixed method approach; results of this analysis will inform future implementation strategies. If successful, this study will provide much-needed evidence regarding the impact of PRS on MOUD treatment retention and will result in a patient-centered PRS program that can be implemented in geographically diverse outpatient MOUD programs, including underserved rural areas that encompass a key health disparities population for OUD.