Naltrexone for Overdose Prevention

Inclusion Criteria: 1. at-risk for HIV or living with HIV 2. stimulant use disorder (by DSM-V) or positive urine drug test for cocaine, amphetamine, or methamphetamine in last 6 months AND report at least 10 days of stimulant use/month, 3. able to provide informed consent, 4. English-speaking, 5. age 18 years old or greater. Exclusion Criteria: 1. prescribed or non-prescribed opioid use (including newly diagnosed opioid use disorder by DSM-V), 2. receipt of long-acting injectable naltrexone for other indications in past 30 days, 3. planned surgery in next 6 months, 4. moderate, severe or chronic liver disease (AST, ALT ≥ 5 times the upper limit of normal or symptoms of current liver disease), 5. persons who are pregnant or breastfeeding, 6. increased risk of bleeding (thrombocytopenia \<50 x 109/L, coagulopathy, or therapeutic anticoagulation), 7. known hypersensitivity to naltrexone or its diluents, or 8. any other reason (e.g. comorbid medical conditions, adherence concerns, lack of interest in naltrexone, etc.) that judged by the study team's discretion, would impede the participant from successfully completing the trial.