ALK21-013: Efficacy and Safety of Medisorb® Naltrexone (VIVITROL®) in Adults With Opioid Dependence

Primary Inclusion Criteria: * Written, informed consent * 18 years of age or older * Current diagnosis of opioid dependence, based on Diagnostic and Statistical Manual of Mental Health Disorders, 4th Ed. (DSM-IV-TR) criteria * Voluntarily seeking treatment for opioid dependence * Completing or recently completed up to 30 days of inpatient treatment for opioid detoxification, and off all opioids (including buprenorphine and methadone) for at least 7 days * Noncustodial, stable residence and phone, plus 1 contact with verifiable address and phone * Significant other (eg, spouse, relative) willing to supervise compliance with the study visit schedule and procedures * Agree to use contraception for study duration if of childbearing potential Primary Exclusion Criteria: * Pregnancy or lactation * Clinically significant medical condition or observed abnormalities (eg: physical exam, electrocardiogram (ECG), lab and/or urinalysis findings) * Positive naloxone challenge test at randomization (Day 0) * Evidence of hepatic failure including: ascites, bilirubin \>10% above upper limit of normal (ULN) and/or esophageal variceal disease * Past or present history of an acquired immunodeficiency syndrome (AIDS)-indicator disease in HIV-infected subjects * Active hepatitis and/or aspartate aminotransferase (AST), alanine aminotransferase(ALT) \>3xULN * Current major depression with suicidal ideation, psychosis, bipolar disorder, or any psychiatric disorder that would compromise ability to complete the study * Recent history (within 6 months prior to screening) of suicidal ideation or attempt * Dependence within prior year based on DSM-IV-TR, to any drugs other than prescription opioids or heroin, caffeine, marijuana, or nicotine * Active alcohol dependence within prior 6 months * Current alcohol use disorder that would, in the Investigator's opinion, preclude successful completion of the study * Positive urine drug test for cocaine, benzodiazepines, or amphetamines at screening * Use of oral naltrexone for 7 consecutive days within 60 days prior to screening * Known intolerance and/or hypersensitivity to naltrexone, carboxymethylcellulose, or polylactide-co-glycolide (PLG)