Inclusion Criteria:

• Aged 18 to 65
• Voluntarily seeking treatment for opioid use disorder (OUD)
• Consistent use of fentanyl or other high potency synthetic opioids
• Meets DSM-5 criteria for OUD with at least moderate severity
• Able to provide written informed consent in English and willing to comply with study procedures

Exclusion Criteria:

• Meets DSM-5 criteria for another substance use disorder as the primary diagnosis
• Has an active, unmanaged psychiatric condition that would make participation hazardous (e.g., acute, psychosis, current suicidality, current manic episode)
• Has an active, unmanaged medical condition that would make participation hazardous or preclude use of buprenorphine or ancillary medications for withdrawal (e.g., unmanaged hypertension, unmanaged diabetes, clinically significant abnormality on ECG, acute hepatitis)
• Buprenorphine or methadone treatment in the past 30 days
• Known allergy, hypersensitivity or intolerance to buprenorphine
• Pregnancy, lactation, or unwillingness to use adequate contraceptive methods
• Current physiological dependence on sedative-hypnotics or alcohol that would require medically supervised detoxification
• Liver function tests > 2x the upper limit of normal
• Use of medications or herbal products with known CYP3A4 inhibition or induction properties in the past 30 days