 The purpose of this study is to assess the safety and effectiveness dextroamphetamine to help methamphetamine users quit or cut down on their use. The study lasts for 9 weeks. Eligible participants will attend research visits twice per week, and will receive individual counseling sessions once per week for all 9 weeks. 50 of the participants will receive the active medication while the other 50 will receive the placebo sugar pill. Neither the participant or the study team will know if the participant is receiving the placebo or active drug. 