Evaluation of the O'Neil Long Acting Naltrexone Implant in Opioid Dependent Persons

Inclusion Criteria: * All genders between 18 and 65 (inclusive) years old * Meet criteria for a current (within the previous 12-months) DSM-5 diagnosis of OUD at screening, and voluntarily seeking relapse-prevention treatment with NTX implant * Completed opioid withdrawal as demonstrated by a negative naloxone challenge test (i.e., has tolerated naloxone 0.8 mg) * Individuals currently treated with NTX will be eligible to receive the implant at the end of the dosing interval of either Vivitrol or oral NTX * Have no medical or psychiatric contraindications to treatment either with NTX or with the OLANI, as determined by the site clinician and based on medical history and current health status * Able to sufficiently speak and understand English and understand study procedures * Able and willing to provide written informed consent * Able and willing to provide detailed contact information for both self and for close contact(s) on the locator form * Able and willing to comply with the requirements and procedures of the protocol, including tolerating a minor surgical procedure with local anesthetic for placement of the implant sets into the subcutaneous tissue of the abdomen * Have an initial weight between 45.3 and 130 kg (inclusive) or have a BMI of 18.5 to 35.0 (inclusive) * For female participants of childbearing potential, a willingness to practice an effective method of birth control for the duration of participation in the study. Acceptable methods of birth control are spe…