Assessing a Clinically-meaningful Opioid Withdrawal Phenotype

Inclusion Criteria: * 18 years - 65 year old * Opioid-positive urine sample * Current opioid use disorder with evidence of physical dependence * Interest in undergoing opioid taper Exclusion Criteria: * Evidence of physical dependence on alcohol or benzodiazepines that requires medical intervention * Being pregnant or breastfeeding * Enrolled in methadone or buprenorphine maintenance treatment * Clinically significant hypotension (\<90/60mmHg) or bradycardia (\<45bpm) * History of myocardial infarction * Subjects who are positive for hepatitis B surface antigen and/or hepatitis C antibody with liver function tests outside the normal range (persons with a positive hepatitis C antibody and normal liver functions tests are NOT excluded from the study) * Significant mental health or physical disorder, or life circumstances, that is expected to interfere with study participation