CLINICAL-EVALUATION AND PLASMA CLOZAPINE CONCENTRATIONS IN CHINESE PATIENTS WITH SCHIZOPHRENIA

The relationships between clozapine dosages, plasma concentrations, an d clinical responses in Chinese schizophrenics were studied. Fourteen treatment-refractory schizophrenic patients were treated with clozapin e for 12 weeks. Patients were assessed before and after 6 and 12 weeks of treatment using the Brief Psychiatric Rating Scale (BPRS), the Cli nical Global Impression (CGI), and the Simpson-Angus Scale for Extrapy ramidal Side Effect. Plasma clozapine concentrations were determined b y high-performance liquid chromatography. Ten patients (71.4%) respond ed after 12 weeks of treatment. Although the mean daily dosage at week 12 (373 +/- 90 mg/day) was lower than that reported in American trial s (444 mg/day), the mean plasma clozapine concentration attained (1,07 8 +/- 385 ng/ml) was higher. This higher concentration may be due to t he lower body weight and the preponderance of women among our patients , absence of smoking and alcohol use, and/or ethnic difference between Chinese and non-Chinese. There was wide interindividual variation in the plasma clozapine concentrations. Compared with other studies, the plasma clozapine concentrations and the response rate were higher. Alt hough the sample size was small, the findings are suggestive of pharma cokinetic and pharmacodynamic ethnic differences in Chinese with cloza pine therapy.