Inclusion Criteria:  Opioid Use Disorder, moderate to severe Ages 22 to 50 Lives in New York City, able to travel for visits Willing to be admitted to an inpatient unit  Exclusion Criteria:  Medical disorder, for who study participation could be deleterious (neurologic, cardiac, renal or infectious disease Hypertension: BP > 150/100 Elevated liver function tests (AST, ALT) > 3x normal Having a painful medical illness for which opioids are needed (including upcoming surgery).