The purpose of the study is to understand the relationship between what an individual inherited from their family (genetics), how they respond and feel after drinking alcohol, and how they respond to pre-treatment with naltrexone, a medication that blocks some of the effects of alcohol and is approved for the treatment of alcoholism. The investigators are conducting this study on those of African descent because there is almost no research focused on this group and the association with genetics. The investigators seek to enroll 40 people in the study. Participation will consist of 4 different alcohol challenge sessions. Each session will be separated by at least 10 days. In total, there will be four challenge sessions.