"This whole thing is relationship medicine": A qualitative analysis of mobile and street-delivered medication for opioid use disorder in King County, Washington, using RE-AIM.

Background: Nationally, drug overdose deaths have increased 3-fold over the past two decades, and as of 2023 were significantly higher in Washington (WA) state. Medication for opioid use disorder (MOUD) reduces morbidity and mortality of opioid use; however, delivery often occurs in clinics with multilevel barriers to care. Mobile and street-based models are strategies for engaging individuals at high risk of an overdose by bringing MOUD directly to people who use drugs (PWUD) in the community. This study used the RE-AIM (Reach Effectiveness Adoption Implementation Maintenance) framework to systematically examine cross-programmatic care delivery and sustainability of mobile and street-based MOUD models in King County, WA. Methods: We conducted semi-structured interviews with frontline providers and administrators between January-June 2025. Eligible programs provided MOUD in King County, WA, and delivered care using a mobile and/or street team model. Using team-based iterative coding, we developed initial codes deductively from REAIM and refined the codebook during consensus coding, allowing inductive codes to emerge. A qualitative descriptive methodology informed by RE-AIM was applied for thematic analysis. Results: Participants (n = 21) were from 13 unique MOUD programs and were mostly female (57%), held a master's degree or higher (67%), and had an average of 7 years of work experience with opioid use disorder. Patients reached were often living unhoused with complex comorbidities and were identified through referrals, outreach, and co-location with social services. Effectiveness was often measured by funder-driven metrics that participants felt focused on clinical and process outcomes rather than accurately capturing patient well-being. Flexibility in training, staff roles, practice, and medication protocols was key to the adoption of MOUD in mobile and street environments. Implementation was facilitated by interdisciplinary teams, the combination of established mobile vans with targeted high-touch outreach, and holistic wraparound care. Programmatic maintenance depended on strong community partnerships and diverse funding streams. Sustainability hinged on program capacity meeting increasing demand and on transitioning clients to clinic care, so outreach efforts could continue to center on PWUD with the highest needs. Conclusions: Programs can leverage these mechanisms to initiate and retain individuals at high risk of opioid overdose with MOUD services.