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Interindividual variability in sensitivity to warfarin‐Nature or nurture?
Author(s) -
Loebstein Ronen,
Yonath Hagith,
Peleg Daria,
Almog Shlomo,
Rotenberg Michal,
Lubetsky Aharon,
Roitelman Joseph,
Harats Dror,
Halkin Hillel,
Ezra David
Publication year - 2001
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1067/mcp.2001.117444
Subject(s) - cyp2c9 , warfarin , genotype , medicine , maintenance dose , pharmacogenetics , allele , endocrinology , vitamin , pharmacology , gastroenterology , biology , cytochrome p450 , metabolism , genetics , atrial fibrillation , gene
Background Interindividual variability in responses to warfarin is attributed to dietary vitamin K, drug interactions, age, or genetic polymorphism in the cytochrome P4502C9 enzyme (CYP2C9) (allelic variants 2C9*2 and 2C9*3 ) linked with impaired metabolism of the potent enantiomere S ‐warfarin. Patients and Methods We quantified the relative effects of age and of simultaneously determined CYP2C9 genotype, plasma warfarin and vitamin K concentrations, and concurrent medications on warfarin maintenance doses in 156 patients at optimized stable anticoagulation. Results Allele frequencies for CYP2C9*1 , CYP2C9*2 , and CYP2C9*3 were 0.84, 0.10, and 0.06. Warfarin doses were 6.5 ± 3.2, 5.2 ± 2.4, and 3.3 ± 2.0 mg/d in the 3 genotype groups ( P < .0001). Warfarin doses decreased with age as follows: 7.7 ± 3.7 versus 4.9 ± 2.9 mg/d at <50 years and >66 years ( P < .001), mainly as a result of decreased plasma warfarin clearance (2.8 ± 1.4 mL/min versus 1.9 ± 0.8 mL/min; P < .001). Vitamin K (1.6 ± 1.1 ng/mL) did not differ among the age or genotype groups. Patients ≥66 years old with the CYP2C9*3 allele required only 2.2 ± 1.2 mg/d compared with 7.9 ± 3.7 mg/d in those ≤65 years old bearing the CYP2C9*1 allele ( P < .001). On multiple regression, warfarin maintenance doses were independently associated with plasma warfarin (reflecting its metabolic clearance) ( r 2 = 0.26), age (possibly reflecting increased intrinsic sensitivity) ( r 2 = 0.12), and genotype (reflecting S ‐warfarin levels) ( r 2 = 0.10) but not with plasma vitamin K. Conclusions At optimized steady state, individual sensitivity to warfarin is determined by CYP2C9 genotype and age with no effect of vitamin K. Prospective studies will determine the impact of these findings in clinical practice. Clinical Pharmacology & Therapeutics (2001) 70 , 159–164; doi: 10.1067/mcp.2001.117444