Marker gene polymorphisms in hyperkinetic disorder - predictors of clinical response to treatment with methylphenidate?

Gene polymorphisms of the dopamine D4 receptor (DRD4) and serotonin transpo rter (5-HTT) are under discussion as potential genetic risk factors for hyp erkinetic disorder (HID). In this disorder, treatment with the psychostimul ant methylphenidate (MPH; Ritalin (R)) induces calming effects and ameliora tion in only 70% of the patients. MPH blocks the reuptake of dopamine, thus enhancing synaptic dopamine which in turn antagonizes the release of prola ctin (PL). Genotyping HD patients for DRD4 and 5-HTT polymorphisms and meas uring PL concentrations, we report on an association between the combinatio n DRD4*7/5HTT LL genotype and a reduced improvement in general functioning accompanied by different PL levels upon MPH treatment. Thus, our study supp orts the hypothesis that marker gene polymorphism may be helpful in identif ying MPH non-responders. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.