Attention Deficit Hyperactivity Disorder (ADHD): Methylphenidate (Ritalin) and Dopamine 625 FOR HKMA CME MEMBER USE ONLY. DO NOT REPRODUCE OR DISTRIBUTE. Attention Deficit Hyperactivity Disorder (ADHD): Methylphenidate (Ritalin) and Dopamine

Attention-deficit hyperactivity disorder (ADHD) is observed in 3–9% of school-aged children and 4% of adults worldwide at higher rates in males than females (2.5:1) and in children older than 9years relative to younger children. Although family, twin, and adoption studies indicate high heritability (0.76), the mode of transmission is unknownbut suspected tobe polygenic. Molecular genetic studies suggest that susceptibility to ADHD involves multiple small-effect genes coding for proteins involved in catecholaminergic transmission. Catecholaminergic etiology is consistent with the treatment of choice for ADHD – psychostimulants such as amphetamines and methylphenidate hydrochloride (MPH) that increase synaptic levels of dopamine and norepinephrine by somewhat different mechanisms. Psychostimulants are highly effective for temporary alleviation of symptoms, starting at 30min and peaking 60–90min following oral administration of immediate-release formulations. Attempts to elucidate the therapeutic efficacy of MPH for ADHD have shaped current hypotheses about the central role of catecholamines, particularly dopamine (DA), in the neuropathophysiology of ADHD.