Relationship between plasma risperidone concentrations and clinical features in chronic schizophrenic patients in China

BACKGROUND Prior studies have noted great variability in the plasma levels of risperidone (RIS). Plasma concentrations of RIS and its active moiety are highly variable and depend on absorption, metabolism, and other predictors of metabolic dysregulation; however, these factors are poorly understood and the association between metabolic change and change in psychopathology is uncertain. AIM To ascertain the characteristics of chronic schizophrenic patients treated with RIS, and to assess their relationship with plasma RIS levels. METHODS This was a descriptive cross-sectional study of 50 patients with a diagnosis of schizophrenic psychosis treated with RIS in a psychiatric service. The plasma concentrations of RIS and its metabolite 9-hydroxyrisperidone were determined by high performance liquid chromatography. The patients' demographic and clinical characteristics, and psychopathologies were assessed, and the associations between clinical variables and plasma levels of RIS were explored. RESULTS Male patients received higher doses of RIS than female ones, but plasma concentrations of RIS and risperidone + 9-hydroxyrisperidone (active moiety) were higher in female patients. Age and the mean scores of the general psychopathology subscale of the Positive and Negative Syndrome Scale (PANSS) were significantly positively correlated with plasma concentrations of risperidone + 9-hydroxyrisperidone adjusted for weight and dose in all 50 subjects. In male subjects, we found a statistically significant positive correlation between the concentrations of risperidone + 9-hydroxyrisperidone in plasma/(dose x kg) and age, mean PANSS negative subscale scores, mean PANSS general psychopathology subscale scores, and mean PANSS total scores. CONCLUSION Long-term use of RIS should be closely monitored in older patients and females to minimize the risk of high concentrations which could induce side effects.