Therapeutic drug monitoring of risperidone and its active metabolite 9-hydroxyrisperidone in the treatment of schizophrenia

AIM: To conduct a routine therapeutic drug monitoring (TDM) and analyze its results for the optimization of pharmacotherapy. MATERIAL AND METHODS: Fifty-six inpatients (in total 68 samples) with various forms of schizophrenia were enrolled. High performance liquid chromatography with mass-spectrometric detection was used for quantitative determination of risperidone and 9-hydroxyrisperidone in the serum. RESULTS: Concentrations of risperidone and 9-hydroxyrisperidone were correlated with drug dose. Total concentrations in the blood at doses from 2 to 8 mg per day were distributed as follows: 44.1% were in the therapeutic, 29.4% in sub-therapeutic ( 60 ng/mL). CONCLUSIONS: Concentrations of risperidone and 9-hydroxyrisperidone did not follow the normal distribution. The results showed that monitoring of the total concentration of risperidone and its metabolite 9-hydroxyrisperidone was an effective tool for testing and quality control for the purpose of individualization of pharmacotherapy.