title: Plasma clozapine levels and clinical response in treatment-refractory Chinese schizophrenic patients.
abstract: OBJECTIVE
  To evaluate clinical efficacy of clozapine in relation with its plasma level in a group of Chinese patients with treatment-resistant schizophrenia. In addition, the relationship between plasma level and side effects were examined.
  
  
  METHODS
  Fifty-one patients with treatment-resistant schizophrenia were put on a fixed dose of clozapine at 300 mg/day for 6 weeks. Non-responders to week 6 received 500 mg/day in subsequent 6 weeks. Responders to week 6 continued to receive 300 mg/day. Clozapine plasma levels were checked at weeks 6 and 12.
  
  
  RESULTS
  No association was found between clozapine plasma level, response and side effects. Sodium valproate was found to elevate clozapine plasma level while lowering norclozapine/clozapine ratio.
  
  
  CONCLUSIONS
  Clozapine plasma level was not found to be associated with response and side effect in Chinese treatment-resistant schizophrenic patients. Various explanations were postulated for the lack of relationship observed between clozapine plasma level and response in this population.
authors.affiliation: Castle Peak Hospital, 15 Tsing Chung Koon Road, Tuen Mun, New Territories, Hong Kong, PR China. jessicaoyw@gmail.com
authors.forename: Jessica Oi-Yin
authors.initials: JO
authors.lastname: Wong
authors.forename: Shung-pun
authors.initials: SP
authors.lastname: Leung
authors.forename: Tony
authors.initials: T
authors.lastname: Mak
authors.forename: Roger Man-kin
authors.initials: RM
authors.lastname: Ng
authors.forename: Kai-tai
authors.initials: KT
authors.lastname: Chan
authors.forename: Henry
authors.initials: H
authors.lastname: Hon-Kee Cheung
authors.forename: Wing-kit
authors.initials: WK
authors.lastname: Choi
authors.forename: Judy
authors.initials: J
authors.lastname: Lai
authors.forename: Alfert
authors.initials: A
authors.lastname: Wai-Kiu Tsang
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000008:administration & dosage; D014150:Antipsychotic Agents / Q000097:blood* / Q000627:therapeutic use*; D002681:China / Q000453:epidemiology; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003024:Clozapine / Q000097:blood* / Q000627:therapeutic use*; D004347:Drug Interactions; D004563:Electrochemistry / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012372:ROC Curve; D012559:Schizophrenia / Q000097:blood* / Q000188:drug therapy*; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D013997:Time Factors; D014635:Valproic Acid / Q000008:administration & dosage
chemical_list: D000927:Anticonvulsants; D014150:Antipsychotic Agents; D014635:Valproic Acid; D003024:Clozapine