This was a Phase 3 multicenter randomized, open-label, safety study assessing the safety of repeat doses of Medisorb® naltrexone 380 mg (VIVITROL®) administered for up to 1 year to adults with alcohol and/or opioid dependence as defined by Diagnostic and Statistical Manual of Mental Health Disorders (DSM-IV) criteria. Eligible subjects were randomized in a 6:1 ratio to receive 1 of the following regimens: a single intramuscular (IM) injection of VIVITROL administered once every 4 weeks or oral naltrexone 50 mg administered daily.