A Clinical Trial Comparing Buprenorphine Formulations for High Potency Synthetic Opioid Use

The goal of this clinical trial is to compare buprenorphine formulations (sublingual buprenorphine versus long-acting injectable buprenorphine) for treating opioid use disorder among individuals who use fentanyl and/or other high potency synthetic opioids. Individuals aged 18-65 will be eligible for enrollment. The main questions it aims to answer are: Are there differences in frequency of drug use after individuals start treatment with sublingual buprenorphine compared to injectable buprenorphine? Are there differences in rates of sustained relapse after individuals start treatment with sublingual buprenorphine compared to injectable buprenorphine? Investigators also seek to understand and explore: How factors like body fat, body weight, and quantity of fentanyl use before treatment influence treatment outcomes. How blood levels of buprenorphine and its metabolite norbuprenorphine early on in treatment may influence treatment outcomes. How factors like craving and opioid withdrawal symptoms influence treatment outcomes. Participants will: Complete a brief overnight hospital stay in an inpatient research unit. This hospital stay will enable participants to start treatment with either sublingual buprenorphine or injectable buprenorphine. Provide blood and urine samples while on the inpatient unit and at follow up. Complete in-person follow up visits at 1-, 2-, 3- and 4-weeks after leaving the hospital to measure drug use, craving, withdrawal, quality of life, and physical health.