Possible relationship between combined plasma concentrations of risperidone plus 9-hydroxyrisperidone and extrapyramidal symptoms. Preliminary study.

We investigated the relationships between extrapyramidal symptoms (EPS) induced by risperidone, the dosage of risperidone and the combined plasma concentrations of risperidone plus its active metabolite, 9-hydroxyrisperidone, in 20 schizophrenic patients. There was a positive correlation between the scores on the Simpson and Angus Scale and both the dosage of risperidone and the sum of the plasma levels of risperidone and 9-hydroxyrisperidone. These results suggest that EPS induced by risperidone increase in conjunction with both the dosage of risperidone and the total plasma concentrations of the parent compound and its active metabolite. Copyright 2001 S. Karger AG, Basel