PROJECT SUMMARY AND ABSTRACT Opioid use disorder (OUD) causes significant morbidity and mortality in the United States. Efficacious pharmacotherapies that can be delivered in a primary care or specialty clinic setting have been developed but most patients with OUD do not receive them. In recent years, three kinds of long-acting medication for OUD (MOUD) have been approved by the Food and Drug Administration (FDA): monthly injectable naltrexone (2010), six-monthly implantable buprenorphine (2016) and monthly injectable buprenorphine (2017). These modalities have several theoretical advantages over daily buprenorphine or methadone – e.g., stabilizes dosing, reduces frequency of follow-up visits, prevents diversion – but their uptake and dissemination in real- world settings have not been characterized. The proposed research will investigate provider- and systems- level barriers and facilitators to adoption of long-acting MOUD. In this mentored career development award (K01), Dr. Shover will characterize clinicians who are early adopters of long-acting MOUD, identify context- specific barriers and facilitators to prescribing and administering long-acting MOUD, and longitudinally compare dissemination of long-acting MOUD to that of daily MOUD. In Aim 1, Dr. Shover will use insurance claims data to characterize individual and organizational attributes of providers who prescribe long-acting buprenorphine or naltrexone to treat OUD in the first year of their FDA approval. In Aim 2, Dr. Shover will conduct qualitative interviews with primary care physicians, pain medicine physicians, and psychiatrists to identify subjective factors that influence willingness or capacity to prescribe long-acting MOUD. In Aim 3, Dr. Shover will conduct a longitudinal analysis of dissemination of long-acting MOUD in their first five years, comparing geographic and systems-level patterns diffusion to those of daily oral MOUD. Through the award, Dr. Shover will build on her doctoral training as an epidemiologist and experience in substance use policy and community-based HIV prevention to develop new skills needed to conduct impactful addiction health services research. These skills will include working with claims data, qualitative interviewing, implementation science, grant-writing, and scientific communication. Through coursework, clinical observation in psychiatry and pain medicine clinics, mentorship, and external conferences and workshops, Dr. Shover will gain the skills needed to apply for her first R01 and pursue a career as a tenure-track principal investigator.