This is a double-blind, placebo-controlled trial of 120 binge-drinking MSM to 12 weeks of naltrexone 50mg, to be taken in anticipation of heavy drinking. Ethnically and racially diverse participants will be recruited using Respondent Driven Sampling as well as active field recruitment. MSM will be seen weekly for alcohol-metabolite urine testing, study drug dispensing, and brief counseling for alcohol use. Safety assessments and behavioral surveys will be completed monthly.

This is a double-blinded, placebo controlled trial of 120 binge-drinking MSM to 12 weeks of naltrexone 50mg, to be taken in anticipation of heavy drinking. Ethically and racially diverse participants will be recruited using venue based recruitment and social network bsed recruitment strategies. Participants will be seen weekly for alcohol metabolite urine testing, study drug dispensing and brief counseling for alcohol use. Safety assessments and behavioral surveys will be completed monthly. Efficacy on alcohol consumption and alcohol-associated sexual risk behavior (Aims 1-3) will be assessed using weekly timeline follow-back, screening for ethyl glucuronide (EtG) positive urines, and computer administered monthly interventions. Tolerability and acceptability (Aim 4) will be assessed through tracking of adverse events and medication adherence. Generalized estimating equation (GEE) models will be fitted to estimate treatment effects on repeated study outcomes.

Inclusion Criteria:

• (1) Male gender (2) self-reported anal sex with men in the prior three months while under the influence of alcohol (3) at least one binge drinking (five or more drinks on a single occasion) session per week in the prior three months; (4) interested in reducing binge alcohol consumption; (5) HIV-negative by rapid antibody test or medical record documentation of HIV infection (HIV positive participants); (6) no current acute illnesses requiring prolonged medical care; (7) no chronic illnesses that are likely to progress clinically during trial participation; (8) able and willing to provide informed consent and adhere to visit schedule; (9) age 18-70 years; (10) baseline complete blood count (CBC), total protein, albumin, glucose, alkaline phosphatase, creatinine, blood urea nitrogen (BUN), and electrolytes without clinically significant abnormalities as determined by study clinician in conjunction with symptoms, physical exam, and medical history.

Exclusion Criteria:

• (1) Any psychiatric (e.g. depression with suicidal ideation) or medical condition that would preclude safe participation in the study; (2) known allergy/previous adverse reaction to naltrexone; (3) current use of/ dependence on any opioids or a known medical condition which currently requires/may likely require opioid analgesics; (4) opioid-positive urine at enrollment; (5) current CD4 count < 200 cells/mm3 (6) moderate/severe liver disease (aspartate aminotransferase (AST), alanine transaminase (ALT) > 3 times upper limit of normal); (7) impaired renal function (creatinine clearance < 50 ml/min); (8) currently participating in another intervention research study with potential overlap; (9) alcohol dependence as determined by Structured Clinical Interview for the Diagnostic and Statistical Manual for Mental Disorders (SCID) criteria (participants with non-dependent alcohol use disorders/symptoms of alcohol abuse (per Diagnostic and Statistical Manual--DSM-IV) are eligible) (10) any condition that, in the principal investigator and/or study clinician's judgment interferes with safe study participation or adherence to study procedures; (11) not having a cell-phone that can send and receive text messages.