The purpose of this study is to learn how best to treat substance use disorders in an HIV clinic setting. Specifically, the purpose of this pilot study is to learn if extended-release naltrexone (XR-NTX) would be a feasible and acceptable treatment for HIV-infected individuals with opioid or alcohol use disorders.

Inclusion Criteria:

1. Meet Diagnostic and Statistical Manual (DSM-5) criteria for moderate or severe opioid use disorder and/or alcohol use disorder.
2. Be willing to be randomized to antagonist-based therapy or treatment as usual (TAU) for treatment of opioid and/or alcohol use disorders.
3. Be HIV-infected as defined by history of positive HIV serology or HIV RNA pcr >10,000 copies/mL).
4. Be willing to establish ongoing HIV care at community treatment program(CTP) if not already receiving ongoing care.
5. Be willing to initiate antiretroviral therapy (ART) if not already prescribed ART, regardless of CD4 count.
6. Be at least 18 years old.
7. Be able to provide written informed consent and HIPAA (if applicable) for medical record abstraction.
8. Be able to communicate in English.
9. If female, be willing to take measures to avoid becoming pregnant.

Exclusion Criteria:

Individuals will be excluded from pilot study participation if they:

• Have a serious medical, psychiatric or substance use disorder that, in the opinion of the study physician, would make study participation hazardous to the participant, compromise study findings, or prevent the participant from completing the study.

Examples include:

1. Disabling or terminal medical illness (e.g., active opportunistic infection, uncompensated heart failure, cirrhosis or end-stage liver disease, acute hepatitis and moderate to severe renal impairment) as assessed by medical history, review of systems, physical exam and/or laboratory assessments;

   1. Severe, untreated or inadequately treated mental health disorder (e.g., active psychosis, uncontrolled manic-depressive illness) as assessed by history and/or clinical interview;
   2. Current severe benzodiazepine or other depressant or sedative hypnotic use requiring medical detoxification;
   3. Suicidal or homicidal ideation requiring immediate attention.

2. Have aspartate aminotransferase (AST) or alanine aminotransferase (ALT) liver enzymes greater than 5 times upper limit of normal on screening phlebotomy. Results from tests conducted within the past 30 days which are abstracted from medical record information are acceptable.

3. Have international normalized ratio (INR) > 1.5 or platelet count <100k. Results from tests conducted within the past 30 days which are abstracted from medical record information are acceptable.

4. Have known allergy or sensitivity to naloxone, naltrexone, polylactide-co-glycolide, carboxymethylcellulose, or other components of the Vivitrol® diluents.

5. Anticipate undergoing surgery during study participation.

6. Have chronic pain requiring ongoing pain management with opioid analgesics.

7. Pending legal action or other reasons that might prevent an individual from completing the study.

8. Currently pregnant or breastfeeding.

9. Body habitus that, in the judgment of the study physician, precludes safe intramuscular injection of XR-NTX, (e.g. excess fat tissue over the buttocks).

10. Received methadone or buprenorphine maintenance therapy for treatment of opioid dependence in the 4 weeks prior to screening.

11. Have taken an investigational drug in another study within 30 days of study consent.

12. Have ECG findings that, in the opinion of the study medical clinician would preclude safe participation in the study. Results from ECGs conducted within the past 30 days which are abstracted from medical record information are acceptable.

13. Have had treatment with XR-NTX for opioid or alcohol dependence in the 3 months prior to screening.