The experiment will last 25 days and will enroll 24 individuals addicted to cocaine. In this three-part experiment, participants will be admitted to the inpatient clinic for an 8-day study session. Following this session, they will be discharged from the clinic for a 1-week washout phase. Participants will then return to the inpatient clinic for another 8-day study session. The two study sessions will be identical. During both sessions, participants will first receive topiramate or placebo for 4 consecutive days. While continuing to receive topiramate or placebo, participants will then also receive intravenous cocaine or placebo for 3 consecutive days.Participants will be monitored by the study physician. Electrocardiograms will be used to monitor heart activity, and blood will be drawn frequently to monitor levels of cocaine and topiramate. Participants will complete standardized questionnaires several times each day to assess mood changes and cognitive function.