Glutamatergic Modulation to Facilitate Naltrexone Initiation in Opioid Dependence

Inclusion Criteria: 1. Active opioid dependence, with at least one positive utox result; no history of opioid overdose; and not currently using methadone or buprenorphine 2. Physically healthy 3. No adverse reactions to study medications 4. 21-60 years of age 5. Capacity to consent and comply with study procedures 6. Seeking treatment Exclusion Criteria: 1. Meets DSM IV criteria for current major depression, bipolar disorder, schizophrenia, any psychotic illness, including substance-induced psychosis, and current substance-induced mood disorder with HAMD \> 12. 2. Physiological dependence on another substance requiring medical management, such as alcohol or benzodiazepines, excluding caffeine, nicotine, and cannabis 3. Pregnant or interested in becoming pregnant 4. Delirium, Dementia, Amnesia, Cognitive Disorders, or dissociative disorders 5. Current suicide risk or a history of suicide attempt within the past 2 years 6. On psychotropic or other medication whose effect could be disrupted by participation in the study 7. Recent history of significant violence (past 2 years). 8. Heart disease as indicated by history, abnormal ECG, previous cardiac surgery. 9. Unstable physical disorders which might make participation hazardous such as end-stage AIDS, hypertension (\>140/90), anemia, active hepatitis or other liver disease (transaminase levels \< 2 X the upper limit of normal will be considered acceptable), or untreated diabetes 10. Previous history of CI-581 abuse, and/or a history of adverse reaction/experience wtih prior exposure to CI-581 or benzodiazepines 11. BMI \> 35, or a history of unmanaged obstructive sleep apnea 12. First degree relative with a psychotic disorder (bipolar disorder with psychotic features, schizophrenia, schizoaffective disorder, or psychosis NOS) 13. History of opioid overdose over the past 2 years requiring medical intervention 14. Currently using methadone or buprenorphine