Objectives : The symptoms of attention-deficit/hyperactivity disorder (ADHD) can be treated with methylphenidate, a potent blocker of the dopamine transporter (DAT). The homozygosity of the 10-repeat allele at dopamine transporter gene (DATI) seems to be associated with a poor response to methylphenidate (MPH) in children with ADHD. In present study, we investigated association between DAT density using I-123N- (3-iodopropen-2-yl) -2 Q -carbomethoxy-3beta- (4-chlorophenyl) tropane (["´I] IPT SPECT) and the homozygosity for 10-repeat allele at DATI, and response to MPH in children with ADHD.
Methods :
Eleven drug-naive children with ADHD were included in the study and treated with MPH for about 8 weeks. After the genotyping and SPECT were performed, we compared DAT density between ADHD children with and without the homozygosity for the 10-repeat allele at DATI and investigated correlation between the homozygosity for the 10-repeat allele and response to MPH.
Results : ADHD children with 10/10 genotype (n=7) had a significantly higher DAT density in basal ganglia than the children without 10/10 genotype (n=4) (Right : z=2.65, p=0.008 ; Left : z=2.65, p=-.0.008). We found that while only 28.6% (217) of the subject with 10/10 genotype showed good response (?50% improvement) to MPH treatment, 100% (4/4) of the subjects without 10/10 genotype showed good response to MPH treatment (X2 test : F´=5.238, df=1, p--0.022).
Conclusion : Our findings support an association between homozygosity for the 10-repeat allele at DATI and the DAT density assessed in vivo and correlation between the homozygosity for the 10-repeat allele and poor response to MPH.
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