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Cytochrome P4502D6 genotype does not determine response to clozapine
M J Arranz1, E Dawson, S Shaikh
1Department of Neuropathology, Institute of Psychiatry, De Crespigny Park, Denmark Hill, London.
British Journal of Clinical Pharmacology
|April 1, 1995
Summary
Genetic variations in the CYP2D6 enzyme do not influence how patients with schizophrenia respond to clozapine treatment. Poor metabolizer status for CYP2D6 was equally distributed among responders and non-responders, indicating no correlation.
Area of Science:
- Pharmacogenomics
- Neuroscience
- Clinical Pharmacology
Background:
- Clozapine, an atypical antipsychotic, treats resistant schizophrenia and is partly metabolized by the cytochrome P450 enzyme CYP2D6.
- CYP2D6 exhibits genetic polymorphism, leading to distinct phenotypes: extensive metabolizers (EM) and poor metabolizers (PM).
Purpose of the Study:
- To investigate the influence of CYP2D6 genotype (EM vs. PM) on patient response to clozapine therapy.
- To determine if allelic variations in CYP2D6 affect treatment outcomes in schizophrenia.
Main Methods:
- Genotyping for CYP2D6 poor metabolizer mutations (alleles A and B) in 123 schizophrenic patients on clozapine.
- Classifying patients as responders or non-responders using the Global Assessment Scale.
- Analyzing the distribution of EM and PM phenotypes within response groups.
Main Results:
- Eight patients were identified as poor metabolizers (homozygous for A and/or B alleles).
- Poor metabolizers were evenly distributed between the responder and non-responder groups.
- No significant correlation was found between CYP2D6 alleles and clozapine response.
Conclusions:
- CYP2D6 genotype does not appear to be a significant predictor of clozapine response in patients with schizophrenia.
- These findings support recent evidence suggesting CYP1A2 plays a more critical role in clozapine metabolism than CYP2D6.