title: Cytochrome P4502D6 genotype does not determine response to clozapine.
abstract: 1. The atypical antipsychotic drug clozapine, used in the treatment of resistant schizophrenia, is metabolized partly by the hepatic cytochrome P450 enzyme CYP2D6. Two phenotypes with respect to the activity of the enzyme are recognized (extensive metabolisers (EM) and poor metabolisers (PM)), resulting from allelic variation in the gene, CYP2D6. 2. Genotype was determined in 123 schizophrenic patients currently being treated with clozapine, in order to determine if EM or PM status influences response to this drug. Patients were divided into responders and non-responders using the Global Assessment Scale, and genotyped for the A and B poor metaboliser mutations by digesting PCR products with HpaII or BstNI. 3. Fifty-nine patients were heterozygous for allele B and for allele A. Eight patients were determined as poor metabolisers since they were homozygous either for A and B. Poor metabolisers were equally distributed between responders and nonresponders and no correlation between CYP2D6 alleles and response to clozapine was found. 4. The results are consistent with recent findings showing that CYP1A2, rather than CYP2D6, is the major enzyme responsible for the metabolism of clozapine.
authors.affiliation: Department of Neuropathology, Institute of Psychiatry, De Crespigny Park, Denmark Hill, London.
authors.forename: M J
authors.initials: MJ
authors.lastname: Arranz
authors.forename: E
authors.initials: E
authors.lastname: Dawson
authors.forename: S
authors.initials: S
authors.lastname: Shaikh
authors.forename: P
authors.initials: P
authors.lastname: Sham
authors.forename: T
authors.initials: T
authors.lastname: Sharma
authors.forename: K
authors.initials: K
authors.lastname: Aitchison
authors.forename: M A
authors.initials: MA
authors.lastname: Crocq
authors.forename: M
authors.initials: M
authors.lastname: Gill
authors.forename: R
authors.initials: R
authors.lastname: Kerwin
authors.forename: D A
authors.initials: DA
authors.lastname: Collier
mesh_terms: D000483:Alleles; D003024:Clozapine / Q000378:metabolism* / Q000494:pharmacology / Q000627:therapeutic use; D019388:Cytochrome P-450 CYP1A2; D019389:Cytochrome P-450 CYP2D6; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D005260:Female; D005787:Gene Frequency; D005838:Genotype; D006720:Homozygote; D006801:Humans; D008297:Male; D006899:Mixed Function Oxygenases / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D010088:Oxidoreductases / Q000235:genetics; D016133:Polymerase Chain Reaction; D012044:Regression Analysis; D012559:Schizophrenia / Q000188:drug therapy / Q000235:genetics*
chemical_list: D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; D019388:Cytochrome P-450 CYP1A2; D019389:Cytochrome P-450 CYP2D6; D003024:Clozapine