Increased urine phenylethylamine after methylphenidate treatment in children with ADHD.

The urine levels of beta-phenylethylamine, 3-methoxy-4-hydroxyphenyl glycol, homovanillic acid, and 5-hydroxyindoleacetic acid were measured to clarify the neurochemical mechanism in attention deficit hyperactivity disorder. beta-Phenylethylamine levels were significantly lower in attention deficit hyperactivity disorder individuals (n = 37) than in controls (n = 21). The 22 children with attention deficit hyperactivity disorder were treated with methylphenidate, and they were further divided into methylphenidate responders (n = 18) and nonresponders (n = 4). beta-Phenylethylamine levels significantly increased after methylphenidate therapy in responders, whereas they did not increase in nonresponders.