IntroductionHospitalizations present an opportunity to initiate naltrexone for patients with alcohol use disorder (AUD). Understanding factors associated with post-hospitalization adherence could inform practice. MethodsThis study is a secondary analysis of a clinical trial in which patients with AUD were randomized to oral (PO) versus long-acting injectable (LAI) naltrexone at hospital discharge. The outcome of this secondary analysis was naltrexone adherence 3 months after discharge, defined as receipt of at least 2 out of 3 monthly injections or the equivalent days of self-reported PO medication use (60 out of 90). We used baseline socio-demographics, substance use history, health status, healthcare utilization, and randomization arm to construct multivariable logistic regression models to identify correlates of adherence. ResultsWe evaluated patients who initiated naltrexone treatment, 124 randomized to PO and 120 to LAI (overall mean age 49 years, 80 % male, 51 % Black, 47 % unhoused, and 91 % with severe AUD). At 3 months, 50 % of patients were adherent. LAI naltrexone (aOR 3.88; 95 % CI 2.17–7.13), recent office visit (aOR 2.01; 95 % CI 1.10–3.72), and age (aOR per 10-year increase 1.37; 95 % CI 1.02–1.88) were associated with increased odds of adherence. Unhoused status (aOR 0.54; 95 % CI 0.30–0.98) and cocaine use (aOR 0.35; 95 % CI 0.17–0.71) were associated with decreased odds of adherence. ConclusionsLAI naltrexone for AUD at hospital discharge was associated with better adherence at 3 months vs PO. Access to LAI naltrexone and targeted interventions for patients with cocaine use or who are unhoused hold potential to improve naltrexone adherence.