Clozapine Plasma Levels and the Relationship to the Genetic Polymorphism in Shizophrenic Patients
Status:
Completed
Trial end date:
2016-12-01
Target enrollment:
Participant gender:
Summary
Approximately 30-60% of all schizophrenia patients who fail to respond to typical
antipsychotics may respond to Clozapine. Clozapine has long been considered the "gold
standard" within the atypical neuroleptic spectrum, backed by years of clinical experience
and research, but uncertainties remain in some aspects of this drug. One such question is the
link between dose, blood levels and patient clinical response. The Clozapine therapeutic
plasma levels range between 250 - 450 ng/mL creating difficulties in using these results in
routine clinical practice. Approximately 30% - 51% of "treatment-resistant schizophrenia"
patients do not fully respond to Clozapine, a poorly understood phenomenon. Factors relevant
to Clozapine-resistance include co-morbidity, drug misuse, poor adherence, inadequate
duration of treatment and inadequate dose/plasma-levels. Pharmacogenetic factors such as
different polymorphisms in involved genes may play a role. Pharmacodynamic and genetic data
appear important in determining the clinical response to Clozapine. Clozapine-treated
patients possessing different 3A4 polymorphisms, may respond differently as compared to other
patients having normal 3A4 alleles. Recently, the CYP2D6 has also been involved in this drug
metabolic pathway. Population pharmacokinetics of clozapine evaluated with the nonparametric
maximum likelihood method. This pharmacogenetic explanation/hypothesis may explain Clozapine-
resistance in schizophrenics.
The high variability in plasma levels requires a large study in order to be able to determine
correlation between clinical efficacy and plasma levels and genotyping. A preliminary study
will enable power analysis and adequate determination of sample size.
Phase:
Phase 4
Details
Lead Sponsor:
Tirat Carmel Mental Health Center
Collaborators:
Beersheva Mental Health Center Ben-Gurion University of the Negev HaEmek Medical Center, Israel Sha'ar Menashe Mental Health Center Sha’ar Menashe Mental Health Center Technion, Israel Institute of Technology The Nazareth Hospital, Israel