0502. Which children with ADHD are likely to respond to methylphenidate (MP)?

Attention-deficit/hyperactivity disorder (ADHD) has become a common diagnosis within our schools and clinical practices. Parents and teachers have been sensitised to the disorder, and it is not unusual for teachers to recommend to parents that their children should be treated with MP. Therapeutic trials of MP are also not unusual i.e. to assess whether a child's behaviour or attention span improves, however in this regard, recent studies have identified bioelectrical and biological markers that are associated with clinical response to MP. Several studies have noted the EEG patterns that are indicative of ADHD (e.g. greater delta and theta activity, less posterior beta activity and less alpha than is seen in controls) and also that MP responders tend to have increased frontal beta activity following treatment whereas non-responders show lower activity in the same region. Interestingly, auditory evoked potentials have also been shown to differentiate between MP responders and non-responders, with response being associated with a fronto-central to parietal (FC2:P4) auditory P300 amplitude ratio >0.5. At a biological level the dopamine transporter gene (DAT1) allele status appears to be a good determinant of MP success. Apparently DAT1 may have 9-repeat or 10-repeat alleles, and children with two copies of the 10-repeat allele tend to respond well behaviourally and clinically (again with increased central and parietal beta activity) whereas 9-repeat carriers did not show the MP response.

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