Stimulant drugs are the first class of compounds reported as effective in the treatment of the behavioral disturbances that are evident in children with ADHD. Stimulants are sympathomimetic drugs structurally similar to endogenous catecholamines. The most commonly used compounds in this class include methylphenidate (Ritalin and others), d-methylphenidate (Focalin), d-amphetamine (Dexedrine), and a mixed amphetamine product (Adderall). These drugs have been shown to enhance dopaminergic and noradrenergic neurotransmission in the central nervous system and peripherally (Volkow et al. 2001). Since the various stimulants have somewhat different mechanisms of action, some patients may respond preferentially to one or another (Greenhill et al. 1998).