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