IMPORTANCE: Rates of opioid use disorder (OUD) and associated mortality in the US remain high. Treatment of OUD with buprenorphine reduces morbidity and mortality. There have been national efforts to expand buprenorphine initiation to the emergency department (ED), where many patients with low treatment access seek medical care. Adoption and trends of emergency clinician buprenorphine prescribing are unknown. OBJECTIVE: To describe emergency clinician buprenorphine initiation for OUD, subsequent prescriptions, and changes over time in California. DESIGN, SETTING, AND PARTICIPANTS: Observational retrospective study of buprenorphine prescriptions in the California Controlled Substance Utilization Review and Evaluation System (CURES) database from January 1, 2017, to December 31, 2022. Any patient aged 18 to 79 years with a California zip code who filled a buprenorphine prescription in CURES and their California prescribers were eligible for inclusion. EXPOSURE: Buprenorphine prescription by an emergency clinician. MAIN OUTCOMES AND MEASURES: Outcomes included (1) the number of patients prescribed buprenorphine
(2) the number of clinicians prescribing buprenorphine
(3) the number and characteristics of buprenorphine prescriptions
(4) the percentage of emergency clinician buprenorphine initiation prescriptions with subsequent linkage to a second prescription and continuous prescriptions, also reported as a continuation ratio
and (5) days and number of initiation prescriptions prior to continuous prescriptions. RESULTS: In this retrospective observational study, 345 024 patients received 3.8 million buprenorphine prescriptions from 21 099 clinicians in California from 2017 to 2022. The mean age of patients at the time of first buprenorphine prescription was 37 years
8187 (67%) were male. Emergency clinicians increased from 2% (n = 78) to 16% (n = 1789) of buprenorphine prescribers in 2017 and 2022, respectively (P <
.001). Buprenorphine initiation prescriptions by emergency clinicians increased from 0.1% (n = 53) to 5% (n = 4493) of all initiation prescriptions in 2017 and 2022, respectively (P = .001). The continuation ratio for patients to receive a second prescription within 40 days of an ED initiation was 2.8 (10 823/3916). The continuation ratio for patients to start 180 days or more of continuous prescriptions within 40 days of ED buprenorphine initiation was 18.3 (10 823/593) and 9.1 within 1 year (5989/655 [2017-2021 data]). CONCLUSIONS AND RELEVANCE: These findings suggest increasing prescription of buprenorphine for OUD by California emergency clinicians from 2017 to 2022, with approximately 1 in 9 patients going on to receive continuous buprenorphine prescriptions within 1 year.