Amphetamine is a central nervous system stimulant that affects chemicals in the brain and nerves that contribute to hyperactivity and impulse control. Amphetamine is used to treat attention deficit hyperactivity disorder (ADHD). The Evekeo brand of amphetamine is used to treat ADHD and also narcolepsy. Evekeo is sometimes used to treat obesity in people who have not lost weight with diets or other treatments.