-Potential subjects will complete a screening, including medical history and physical, laboratory, EKG, assessment of MA and other drug use, psychiatric screening and cognitive testing, to determine eligibility. Eligible subjects will repeat the cognitive testing instruments prior to starting medication. After completing the screening period, subjects who continue to be eligible will receive 7 days of oral risperidone to assess tolerability followed by administration of long-acting injectable risperidone, 25mg. For 3 weeks following the first IM injection, participants will take oral risperidone each night to achieve a therapeutic plasma level of risperidone. During the oral co-administration phase, participants will have medication pill counts during their weekly visit to evaluate adherence and corroborate self-report data. Participants will receive additional 25mg risperidone injections every 14 days (at weeks 2, 4, and 6 after the first injection).