Serum concentrations, therapeutic response and side effects in children and adolescents with impulsive-aggressive symptoms during risperidone therapy.

INTRODUCTION: The aim of this prospective naturalistic study was to examine for the first time the relationship between dosage, serum concentration and clinical outcome in children and adolescents with impulsive-aggressive symptoms during risperidone therapy.

METHODS: Steady state trough serum concentrations of risperidone and 9-hydroxyrisperidone (the active moiety) were measured in 103 subjects. The therapeutic effect was assessed by the clinical global impression improvement subscale and side effects by the Udvalg for Kliniske Undersogelser-side effect rating scale.

RESULTS: We found a linear relationship between the risperidone dose and the serum concentration of the active moiety (Spearman rho=0.53) and no correlation between the serum concentration and either the therapeutic effect or side effects. There was no effect of gender and co-medication.

DISCUSSION: This study has the typical limitations of naturalistic studies, therefore our results should be interpreted with caution. Based on the serum concentrations at the therapeutically effective dose range (0.25-1.5 mg/day) we obtained first information on a possibly appropriate therapeutic serum range for the risperidone treatment of children and adolescents with impulsive-aggressive symptoms. Further studies with greater sample sizes are needed to validate our results and to examine the influence of genetic polymorphisms on the serum concentration of risperidone.