Outpatient Low-Dose Initiation of Buprenorphine for People Using Fentanyl.

Importance: The rise of high-potency opioids such as fentanyl makes buprenorphine initiation challenging due to the risks of precipitated withdrawal, prompting the exploration of strategies, such as low-dose initiation (LDI) of buprenorphine. However, no comparative studies on LDI outcomes exist. Objective: To evaluate outpatient outcomes associated with 2 LDI protocols of buprenorphine among individuals with opioid use disorder (OUD) using fentanyl. Design, Setting, and Participants: This cohort study analyzed data on adults with OUD who self-reported daily fentanyl use and underwent buprenorphine initiation using LDI. Data were extracted from the electronic health records of 2 substance use disorder treatment clinics using a specialty behavioral health pharmacy in San Francisco, California, from May 2021 to November 2022. Exposures: Type of LDI protocol selected by individuals: 4-day or 7-day protocol. Main Outcomes and Measures: The primary outcome was successful buprenorphine initiation, defined as self-reported LDI completion and pickup of a refill maintenance prescription, and buprenorphine retention. Logistic regression with generalized estimating equations assessed associations between LDI protocol (4-day vs 7-day) and successful initiation, adjusting for multiple attempts, age, gender identity, race and ethnicity, and housing status. Kaplan-Meier survival curves were used to estimate buprenorphine retention, and survival curves were adjusted using a fitted Cox proportional hazards regression model. Results: A total of 126 individuals (median [IQR] age, 35 [29-44] years; 90 identified as men [71%]; 26 [21%] identified as Black or African American, 20 [16%] as Latine, and 66 [52%] as White individuals) with 175 initiation attempts were included. Across attempts, 72 (41%) had a 4-day LDI protocol and 103 (59%) had a 7-day protocol. Initiation was successful in 60 attempts (34%), including 27 (38%) among 4-day protocol and 29 (28%) among 7-day protocol attempts. Buprenorphine retention rate at 28 days was 21% for a 4-day protocol and 18% for a 7-day protocol. Logistic regression found no significant differences between LDI protocols and successful initiation, while repeated LDI attempts had lower odds of success (second attempt: adjusted odds ratio [AOR], 0.30 [95% CI, 0.14-0.66]; third or more attempt: AOR, 0.22 [95% CI, 0.09-0.53]). Unadjusted and adjusted survival models did not detect a significant difference in retention between LDI protocol types. Conclusions and Relevance: This cohort study found that among people with OUD using fentanyl and attempting outpatient LDI of buprenorphine, successful buprenorphine initiation and retention rates were low. Future studies should examine interventions to improve LDI success and increase buprenorphine uptake and retention.