Evaluating Naltrexone for Use in Conjunction With Buprenorphine in Adults With Opioid Use Disorder Transitioning From Buprenorphine Maintenance Prior to First Dose of VIVITROL

Inclusion Criteria: * Willing and able to provide informed consent * Willing and able to provide government-issued identification * Has a Body Mass Index (BMI) of 18.0-40.0 kg/m\^2 * Has a history of opioid use disorder diagnosis for at least 6 months * Has a history of prescribed buprenorphine (or buprenorphine/naloxone) maintenance for the prior 3 or more consecutive months and is currently buprenorphine-maintained * Must be voluntarily seeking treatment for opioid use disorder and be motivated to receive antagonist therapy * Willing to abide by the contraception requirements for the duration of the study * Additional criteria may apply Exclusion Criteria: * Is pregnant, planning to become pregnant or breastfeeding during the study * Has a positive urine drug screen for opiates or oxycodone at screening * Has used methadone within 30 days prior to study Day -5 * Has used naltrexone (oral or VIVITROL) within the 90 days prior to Day -5 * Has a history of seizures or has received anticonvulsant therapy within the past 5 years for treatment of seizures (use of anticonvulsant during the past detoxification is not exclusionary) * Has a condition, disease state, or previous medical history that would preclude safe participation in the study or affect the ability to adhere to the protocol visit schedule, requirements, or assessments * Has a current diagnosis of schizoaffective disorder, bipolar disorder, or untreated and unstable major depressive disorder * Is currently physiologically dependent on any psychoactive substance (except opioids, caffeine, or nicotine) requiring medical intervention for detoxification * Has a history of hypersensitivity or adverse reaction to buprenorphine, naltrexone, VIVITROL, or naloxone * Additional criteria may apply