Opioid Relapse & HIV Risk: 48 Versus 24 Weeks of Injectable Extended Release Naltrexone

Inclusion Criteria: * HIV-negative men and women 18 years of age or older who meet the Diagnostic and Statistical Manual of Mental Disorders 4th edition-Text Revision (DSM- IV-TR) criteria for opioid dependence * Must be voluntarily seeking treatment for opioid dependence, with injection heroin as the drug and administration route of choice * Must report sharing injection equipment during the past year * Must have successfully completed inpatient detoxification at the Federal Medical Research Center for Psychiatry and Narcology (FMRCPN) * Must have no current evidence of physiologic dependence * Must have a stable address in Moscow with a telephone number where they can be reached * If female, must have a negative pregnancy test and use of medically acceptable contraception if of childbearing age * Must be able to provide informed consent as judged by the ability to read the consent and correctly answer 9 out of 10 questions about the study on a quiz Exclusion Criteria: * No current condition of psychosis (schizophrenia,paranoid disorder, mania) * No history of major psychiatric disorders such as Schizophrenia, Major Depression with suicidal attempts, Bipolar I, uncontrolled epilepsy or other seizure disorder * No current dependence (within the past year) to drugs other than prescription opiates or heroin, caffeine, marijuana, or nicotine based on the Diagnostic and Statistical Manual of Mental Disorders-Text Revision (DSM -IV-TR) criteria * No current alcohol dependence or alcohol use disorder that would preclude successful completion of study procedures * No current suicidal or homicidal ideation requiring immediate attention as determined at baseline assessment * No cognitive impairment with inability to read and understand the consent * No significant laboratory abnormality such as haemoglobin \<10, hepatic transaminase levels \>3 times upper limit of normal or serum creatinine that is \>1.5 times upper limit of normal * No legal charges with impending incarceration * No concurrent participation in another treatment study * Cannot be scheduled for surgery or be likely to require opioids for pain control in next 2 years * Not currently taking naltrexone or currently receiving other treatment (pharmacological or behavioral) for drug dependence or currently receiving psychoactive medication * Cannot have had receipt of any approved or investigational depot product administered into the gluteal muscle within 6 months before screening * Cannot be on any excluded medication at screening or be anticipating the use of an excluded medication during the study period * Cannot have participated in a clinical trial of a pharmacological agent within 30 days prior to screening