title: Influence of cytochrome P-450 CYP2C9 polymorphisms on warfarin sensitivity and risk of over-anticoagulation in patients on long-term treatment.
abstract: Cytochrome P-450 2C9 is the principle enzyme that terminates the anticoagulant effect of warfarin. Genetic polymorphisms in CYP2C9 producing variants with altered catalytic properties have been identified. Patients (n = 561) with a target international normalized ratio (INR) of 2.5 who had been treated with warfarin for more than 2 months were anonymously genotyped for the wild-type CYP2C9*1 allele and the 2C9*2 and 2C9*3 variants. The mean maintenance dose of warfarin in patients who were wild-type for both alleles was 5.01 mg. The maintenance dose of warfarin was significantly related to genotype (Kruskall-Wallis, chi(2) = 17.985, P =.001) with mean maintenance doses in patients with variant alleles between 61% and 86% of that in wild-type patients. The odds ratio for the 2C9*2 allele in patients with a maintenance dose of 1. 5 mg or less was 5.42 (95% CI 1.68-17.4). The odds ratio for one or more variant alleles in patients developing an INR of 8.0 or greater was 1.52 (95% CI 0.64-3.58). The SD of the mean INR, percentage of high INRs, and person-time spent in range were determined as parameters of stability. There was no difference between patients grouped according to genotype for any parameter of stability. This study confirmed an association between CYP2C9 genotype and warfarin sensitivity. However, the possession of a variant allele does not increase the likelihood of severe over-anticoagulation or stability of anticoagulation during long-term therapy. (Blood. 2000;96:1816-1819)
authors.affiliation: Department of Haematology, Addenbrooke's NHS Trust, Cambridge, United Kingdom.
authors.forename: J
authors.initials: J
authors.lastname: Taube
authors.forename: D
authors.initials: D
authors.lastname: Halsall
authors.forename: T
authors.initials: T
authors.lastname: Baglin
mesh_terms: D000483:Alleles; D000925:Anticoagulants / Q000009:adverse effects* / Q000627:therapeutic use; D001189:Aryl Hydrocarbon Hydroxylases; D001777:Blood Coagulation / Q000187:drug effects; D015331:Cohort Studies; D065729:Cytochrome P-450 CYP2C9; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics*; D004305:Dose-Response Relationship, Drug; D005838:Genotype; D006801:Humans; D019934:International Normalized Ratio; D011110:Polymorphism, Genetic; D012307:Risk Factors; D013223:Statistics as Topic; D039181:Steroid 16-alpha-Hydroxylase; D013250:Steroid Hydroxylases / Q000235:genetics*; D013997:Time Factors; D014859:Warfarin / Q000009:adverse effects* / Q000627:therapeutic use
chemical_list: D000925:Anticoagulants; D014859:Warfarin; D003577:Cytochrome P-450 Enzyme System; D013250:Steroid Hydroxylases; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases; D039181:Steroid 16-alpha-Hydroxylase