Safety and Efficacy Study of Vigabatrin to Treat Methamphetamine Dependence

This is a Phase II, randomized, double-blind, placebo-controlled, intent-to-treat, 2-arm, parallel design, multicenter study to evaluate vigabatrin as a treatment for methamphetamine addiction. The study will involve approximately 180 subjects (90/group) who meet DSM IV criteria for methamphetamine dependence. Subjects will be evaluated for their compliance with protocol inclusion/exclusion criteria during Screening/Baseline Phase, lasting up to 4 weeks. At the conclusion of the Screening/Baseline Phase, subjects meeting all inclusion/exclusion criteria will be randomized to one of two treatment groups: vigabatrin or placebo. Subjects will proceed to a 12 week Treatment Phase and then undergo a 12 week follow-up period. Subjects will be scheduled for clinic visits 3 times per week for efficacy and/or safety assessments during the Screening/Baseline Phase and the 12 week Treatment Phase. Subjects will return for follow up visits at Weeks 13, 16, 20 and 24.