Study to Evaluate the Likeability, Safety, and Abuse Potential of NRP 104 in Adults With Histories of Stimulant Abuse

This research is being done to evaluate if NRP104 is a safe drug. The other purpose is to learn if NRP104 produces a high and any other effects like amphetamine and other stimulant drugs that are abused. This information will give some indication if NRP104 can be abused. NRP104 is an investigational drug. This means that it has not been approved by the U.S. Food and Drug Administration (FDA). Healthy people, between the ages of 18 and 55 with histories of substance abuse that include stimulant drugs, may join. Amphetamines are drugs that are used most often to treat attention deficit hyperactivity disorder (ADHD) in children, to treat narcolepsy (excessive sleepiness) and for weight loss.