Treatment: Subjects will randomly be assigned to Group 1 (A/B) or Group 2 (B/A) after completion of Phase I and its subsequent washout period (Figure 1, periods 1 and 2). Group 1 will receive acamprosate (Campral) at a dose of 666 mg. three times daily for 24 weeks followed by a 4-week washout period and then by taking matched placebos for next 24 weeks. Group 2 will receive placebo for 24 weeks followed by a washout and 24 week acamprosate trial. The experiment will be double-blinded. The subjects will know that they could be taking either a placebo or acamprosate. To insure subjects are blind to the intervention, the Campral will be placed in identical capsules to those used for the cellulose placebos that will be produced for the study.