BACKGROUND: Buprenorphine is an effective treatment for opioid use disorder (OUD); however, buprenorphine initiation can be complicated by withdrawal symptoms including precipitated withdrawal. There has been increasing interest in using low dose initiation (LDI) strategies to reduce this withdrawal risk. As there are limited data on withdrawal symptoms during LDI, we characterize withdrawal symptoms in people with daily fentanyl use who underwent initiation using these strategies as outpatients. METHODS: We conducted a retrospective chart review of patients with OUD using daily fentanyl who were prescribed 7-day or 4-day LDI at 2 substance use disorder treatment clinics in San Francisco. Two addiction medicine experts assessed extracted chart documentation for withdrawal severity and precipitated withdrawal, defined as acute worsening of withdrawal symptoms immediately after taking buprenorphine. A third expert adjudicated disagreements. Data were analyzed using descriptive statistics. RESULTS: There were 175 initiations in 126 patients. The mean age was 37 (SD 10 years). 71% were men, 26% women, and 2% non-binary. 21% identified as Black, 16% Latine, and 52% white. 60% were unstably housed and 75% had Medicaid insurance. Substance co-use included 74% who used amphetamines, 29% cocaine, 22% benzodiazepines, and 19% alcohol. Follow up was available for 118 (67%) initiations. There was deviation from protocol instructions in 22% of these initiations with follow up. 31% had any withdrawal, including 21% with mild symptoms, 8% moderate and 2% severe. Precipitated withdrawal occurred in 10 cases, or 8% of initiations with follow up. Of these, 7 had deviation from protocol instructions; thus, there were 3 cases with follow up (3%) in which precipitated withdrawal occurred without protocol deviation. CONCLUSIONS: Withdrawal was relatively common in our cohort but was mostly mild, and precipitated withdrawal was rare. Deviation from instructions, structural barriers, and varying fentanyl use characteristics may contribute to withdrawal. Clinicians should counsel patients who use fentanyl that mild withdrawal symptoms are likely during LDI, and there is still a low risk for precipitated withdrawal. Future studies should compare withdrawal across initiation types, seek ways to support patients in initiating buprenorphine, and qualitatively elicit patients withdrawal experiences.

OBJECTIVES: Fear and risk of precipitated withdrawal are barriers for initiating buprenorphine in individuals with opioid use disorder, particularly among those using fentanyl. A buprenorphine rapid overlap initiation (ROI) protocol (also knownas rapidmicro-dosing) utilizing small, escalating doses of buprenorphine can overcome this barrier, reaching therapeutic doses in 3 to 4 days. We sought to demonstrate the feasibility of implementing a buprenorphine ROI protocol for buprenorphine initiation in the outpatient setting. METHODS: We conducted a retrospective chart review of patients prescribed an outpatient ROI protocol at the Office-based Buprenorphine Induction Clinic from October to December 2020. The ROI protocol utilizes divided doses of sublingual buprenorphine tablets and blister packaging for easier dosing. Patients were not required to stop other opioid use and were advised to follow up on day 4 of initiation. RESULTS: Twelve patients were included, of whom eleven (92%) were using fentanyl at intake. Eleven patients picked up their prescription. Seven patients returned for follow-up (58%), and all 7 completed the ROI protocol. One patient reported any withdrawal symptoms, which were mild. At 30 days, 7 patients (58%) were retained in care, and 5 (42%) were still receiving buprenorphine treatment, 4 (33%) of whom had been abstinent from nonprescribed opioid use for ≥2 weeks. CONCLUSIONS: The ROI protocol was successful in initiating buprenorphine treatment for patients in our outpatient clinic, many of whom were using fentanyl. The ROI protocol may offer a safe alternative to traditional buprenorphine initiation and warrants further study.

Fentanyl-mixed and substituted heroin is well-documented, but less is known about unintentional fentanyl use among people using stimulants. To determine the prevalence of and racial and ethnic disparities in unintentional fentanyl use among people experiencing a medically attended opioid overdose, we reviewed 448 suspected non-fatal overdose cases attended by a community paramedic overdose response team in San Francisco from June to September 2022. We applied a case definition for opioid overdose to paramedic records and abstracted data on intended substance use prior to overdose. Among events meeting case criteria with data on intended substance use, intentional opioid use was reported by 57.3%, 98.0% of whom intended to use fentanyl. No intentional opioid use was reported by 42.7%, with most intending to use stimulants (72.6%), including methamphetamine and cocaine. No intentional opioid use was reported by 58.5% of Black, 52.4% of Latinx, and 28.8% of White individuals (p = 0.021), and by 57.6% of women and 39.5% of men (p = 0.061). These findings suggest that unintentional fentanyl use among people without opioid tolerance may cause a significant proportion of opioid overdoses in San Francisco. While intentional fentanyl use might be underreported, the magnitude of self-reported unintentional use merits further investigation to confirm this phenomenon, explore mechanisms of use and disparities by race and ethnicity, and deploy targeted overdose prevention interventions.