A missed opportunity: receipt of medication for opioid use disorder in Southern California acute care settings

BACKGROUND: Medications for opioid use disorder (MOUD) reduce overdose risk and improve outcomes, yet receipt remains low in acute care settings, including among patients engaged in health care. Understanding sociodemographic and clinical factors associated with lower odds of MOUD receipt is essential to inform strategies that expand access and strengthen responses to the opioid epidemic in the United States. OBJECTIVE: To describe sociodemographic and clinical characteristics and estimate factors associated with lower odds of MOUD receipt among patients with opioid-related diagnoses (ORD) care involvement who had an assigned primary care provider and who utilized acute care settings within a large academic health system in Southern California. METHODS: We analyzed electronic health records from 4,242 patients who had ≥ 1 acute care encounter and a UC San Diego Health-assigned primary care provider between April 22, 2022, and April 21, 2025. Patients were classified as having ORD clinical involvement if they had a documented ICD-10 ORD, an MOUD prescription within 6 months prior to the index acute care encounter, an MOUD prescription during the index acute care encounter, or an opioid overdose-related encounter. Descriptive statistics characterized the sample; logistic regression estimated odds of limited MOUD receipt. RESULTS: Among patients with opioid-related involvement who had an assigned primary care provider and utilized acute care services, 428 (10.1%) received MOUD during the acute care encounter. Prior MOUD prescription within six months preceding the index acute care encounter was associated with the highest odds of MOUD receipt (aOR = 24.11, 95% CI [18.60, 31.53], p < 0.001). Having other substance-related diagnoses was also associated with higher odds of MOUD receipt (aOR = 1.85, 95% CI [1.29, 2.69], p < 0.001). In contrast, patients with any mental health diagnosis had lower odds of MOUD receipt (aOR = 0.73, 95% CI [0.57, 0.94], p = 0.02). Although overdose-related encounters were associated with lower odds of MOUD receipt (aOR = 0.56, 95% CI [0.29, 1.00], p = 0.06), the association did not reach statistical significance after adjustment. CONCLUSION: Significant gaps persist in MOUD receipt among patients with opioid-related involvement in acute care settings. Prior MOUD prescription was strongly associated with MOUD receipt, suggesting barriers in receipt among patients without previous prescriptions. Patients with mental health comorbidity had lower odds of MOUD receipt. Although overdose-related encounters were associated with lower adjusted odds of MOUD receipt, additional research is needed to better understand barriers to MOUD initiation following overdose-related encounters. Overall, these findings call for tailored strategies such as addiction consultation services, peer navigation programs, integrated addiction and behavioral health services, and low-barrier MOUD initiation protocols within acute care settings.