32 DOSE DEPENDENT EFFECTS OF METHYLPHENIDATE ON HYPERACTIVE CHILDREN

Abstract

The clinical problem of hyperactivity is primarily regarded as an attentional deficit. The purpose of this study was to investigate the nature of this attentional deficit and the effect of various dosage schedules of methylphenidate (MP) upon it. 41 hyperactive (HA) children, ages 7-11 years, were tested prior to drug, at two week intervals for eight weeks, after eight weeks on maximum dosage, and after two weeks off drug. Initial dosage was .2 mg/kg and, in the absence of adverse effects, was increased by .2 mg/kg every two weeks up to .8 mg/kg/day. 33 of the 41 subjects were judged to successfully respond to MP . There was a significant improvement in parent and teacher's rating scores and a significant increase in accuracy in attentional performance from pre-drug to end of drug treatment; further there were significant decrements in these measures during the off-drug period. The mean dosage at which greatest response was obtained was .4-.5 mg/kg. Increasing dosage beyond this range did not improve ratings or performance for most drug responders. These findings provide objective evidence that methylphenidate often improves the ability to sustain attention, decreases impulsive responding, and improves behavior as rated by parents and teachers. Such improvement is achieved with relatively low dosage schedules. Higher doses are associated with the appearance of adverse personality changes, such as nervousness, apathy, and aggression, and defeat the purposes of improving school or social adaptation of hyperactive children.