Stimulant medications are prescribed to treat children, adolescents, or adults diagnosed with attention deficit hyperactivity disorder (ADHD). Stimulants block the reuptake of norepinephrine and dopamine in the synapse and increase the overall level of these substances in the brain, but they have a paradoxical calming effect and improve the ability to focus and concentrate for individuals diagnosed with ADHD. Common stimulants used to treat ADHD include methylphenidate, amphetamine, dextroamphetamine, and lisdexamfetamine dimesylate. Stimulant medications are safe when prescribed with close supervision, but they are a Schedule II controlled substance because they have a high potential for misuse and dependence.