Naltrexone in AUD Reward Drinkers

Study eligibility is determined at an initial screening visit, which can be completed in a single day or divided over multiple days. Portions of the screening may occur by telephone or video conference. Participants are asked not to drink before this and at all study visits. At all study visits, study staff will check breath alcohol level using a breathalyzer. If the breath alcohol level is greater than 0.02% (which can result from a single standard drink), participants may not be able to complete the visit. Screening Visit: The screening visit will determine whether the study is a good fit for participants. It take about three hours to complete. * Participants will be asked to show legal photo ID and undergo a breathalyzer test to ensure that the breath alcohol level is below 0.02% to complete this visit. A reading test wil be given to evaluate participant's ability to understand the consent form and study assessment questionnaires. * Once the informed consent is complete a study clinician will complete a medical history and perform a physical examination. Study staff will draw approximately 3 tablespoons of blood for standard laboratory tests. Participants will also be asked to provide a urine sample to conduct a urinalysis, drug screen, and a urine pregnancy test (only for for women of childbearing potential--i.e., who have not had a hysterectomy, bilateral removal of the ovaries, or a tubal ligation or is less than two years postmenopausal). We will not include women who are pregnant, breast-feeding. * Eligible participants will be required to provide the names and contact information of one or two people (trusted friends or family members) who may serve as additional contacts to assist staff with locating participants for safety or other study-related reasons. * Participants will be asked to complete 4 assessments of about psychological health and alcohol and drug use history. First Study Drug Visit (Week 1): Staff will contact participants within 1 week after completing the screening visit to inform eligibility status and schedule the next study visit. * This visit will take approximately one and one-half hours to complete. * Participants will be asked to complete a breathalyzer test and study staff will measure weight and vital signs (blood pressure and heart rate). * Woman of childbearing potential, will be asked to provide a urine sample for a pregnancy test. * Participants will be asked to complete 11 assessments about psychological health and alcohol and drug use history. * Staff will instruct participants how to use the interactive voice response (IVR) system via telephone. During the 8 weeks of the study, participants will be asked to call a toll-free phone number each day, between 5:00 and 8:00 p.m. to connect to the system. Access to the system via a touch-tone phone requires a study ID and a password. The system has prompts to answer questions about feelings and use of alcohol on the day of the call and the preceding day. It takes about 5 to 8 minutes to complete the daily interview. The IVR system will provide a reminder if a call has not been completed by 8:15 p.m. * The first brief counseling session will last about 45 minutes. The study nurse will discuss a treatment goal either to drink less or become completely abstinent. The nurse will also encourage participants to consider ways to reduce or stop drinking, based upon the treatment goal. * Participants will be assigned to receive an injection of study medication administered by the nurse, which will be either XR-NTX or placebo (an inactive substance). The decision as to which medication received will be random, like a flip of a coin. The XR-NTX or placebo will look the same. Neither participants nor any of the study personnel will know which medication is received. In an emergency, though, the study staff in charge of the study medication can be contacted for that information. * At each visit, study staff will ask about any side effects or other adverse events. Biweekly Visits (Weeks 2, 4, and 6): At each biweekly visit: * The staff will check breath alcohol concentration (Breathalyzer), weight, and vital signs and ask about any side effects or other adverse events that were experienced. * Participants will asked to complete 6 assessments about psychological health and alcohol and drug use history. These should take about 20 minutes to answer. * Participants will receive brief counseling from the study clinician, which will last about 20 minutes. * At week 4, woman of childbearing potential, will have another urine pregnancy test. If the urine permanency test is positive, staff will discontinue the medication and the participant will be referred to an obstetrician for care. * At week 4 the study nurse will give the second injection of XR-NTX or a placebo (an inactive substance) * Participants will continue to call and complete the toll-free IVR number nightly. 4\. Endpoint Visit (Week 8): At this visit: * The staff will measure breath alcohol concentration (Breathalyzer), weight, and vital signs and asked about any side effects or other adverse events that may have experienced. * The study staff will ask you to complete 11 assessments about your psychological health and your alcohol and drug use history. These should take about 45 minutes to complete. * Study staff will draw 1 tablespoonful of blood for lab tests. * Participants will receive brief counseling from the study clinician, which will last about 20 minutes. Follow-up Visits (4 weeks after endpoint visit): At the follow-up visit (which will take about one hour), the study staff will: * Check breath alcohol concentration (Breathalyzer), weight and vital signs. * Draw 1 tablespoonful of blood for lab tests. * Participants will be asked to complete 9 assessments about psychological health and alcohol and drug use history. * Once participants have completed the study, they will have an option to receive a letter to inform them whether they received XR-NTX or placebo medication. Early Termination Visit • Participants who choose to withdraw from the study before participation is complete will be asked to return to the research center for a visit to allow staff to administer the end-of-study procedures.