Plasma Concentration of Risperidone: Correlation with Clinical Response in Patients with Schizophrenia

Background: Determination of plasma concentration of antipsychotic drug may provide a valuable tool in dose adjustment and therapeutic efficacy but studies in this area are limited and controversial. Purpose: To assess the relation between plasma concentration of Risperidone and its active metabolite (Paliperidone) and clinical response in Egyptian patients with schizophrenia. Patients and methods: One hundred inpatients diagnosed with schizophrenia were enrolled in the study. Fifty inpatients (33 males, 17 females, with age between 20- 60) completed the study. Risperidone was given in two fixed dose: 6 mg daily (Group I) and 8 mg daily (Group II) for three months. Positive and Negative Syndrome Scales (PANSS) were used for determination of psychopathological state and High- performance liquid chromatography (HPLC) was used for measurement of plasma concentration. These assessments were performed at 1 and 3 months. Results: A highly significant decrease was found in PANSS subscales and total score at 1 and 3 months (P 0.05). Conclusion: Measuring plasma concentration of Risperidone is not useful to enhance efficacy of treatment at 1 or 3 months. More research is required for assessment of other factors affecting the efficacy of Risperidone e.g., receptor occupancy and pharmacogenetics.