Substance use, particularly the compulsive behaviors associated with addiction, lead to unhealthy behaviors including non-adherence to antiretroviral therapy (ART) and treatment failure. High on the list of disorders leading to non-adherence is heroin addiction as a wide range of impulsive, high-risk behaviors accompanies it. The science of adherence would be improved by developing new methods to prevent relapse to heroin addiction, especially methods that can be used in settings that are not limited by the aims to test such a method using an implantable naltrexone formulation (IN) that is approved in Russia and blocks opioid effects for 3 months. The efficacy of the IN should be better than oral naltrexone (ON) because it does not depend on daily behavior to take a tablet and maintains a constant plasma level for months, which should result in sustained blockade, less relapse, and better ART adherence and treatment response.