Extended-release Buprenorphine as a Novel Low-dose Induction Strategy

Who May Qualify: - English speaking adults aged 18 and above. - diagnosis of opioid use disorder. - Self-reporting use of illicit opioids in \>21 days in the prior 30 days. - Provide urine toxicology testing positive for fentanyl at baseline. Who Should NOT Join This Trial: - Seeking medication treatment for opioid use disorder with sublingual buprenorphine or methadone. - Received buprenorphine or methadone treatment in prior 30 days. - Current diagnosis of alcohol or sedative/hypnotic use disorder. - Positive urine drug screen for benzodiazepines, alcohol and or methadone. - Physical dependence on alcohol or sedative/hypnotics. - Psychotic disorder, active suicidality or homicidally or any psychiatric condition that impair ability to provide willing to sign a consent form. - Have a history or diagnosis of Intracranial mass/bleed, seizure disorder, liver cirrhosis, renal failure, obstructive lung disease, hyperthyroidism, narrow-angle glaucoma, valvular heart disease, cardiac arrhythmias, heart failure. - Recent (within 6 months) head trauma, stroke, or myocardial infarction - Requiring treatment with opioids for acute or chronic pain. - History of hypersensitivity or allergy to buprenorphine or fentanyl. - Pregnant or breastfeeding. - Liver function test greater than 3 times upper normal limit. - Receiving medications that are strong or moderate CYP34A inducers or inhibitors (including but not limited to ketoconazole, itraconazole, clarithromycin, fluconazole, erythromycin), in the past 30 days. Always talk to your doctor about whether this trial is right for you.