Genetic factors (VKORC1, CYP2C9, EPHX1, and CYP4F2) are predictor variables for warfarin response in very elderly, frail inpatients

• Published in: Clinical pharmacology and therapeutics Vol. 87; no. 1; p. 57
• Main Authors: Pautas, E, Moreau, C, Gouin-Thibault, I, Golmard, J-L, Mahé, I, Legendre, C, Taillandier-Hériche, E, Durand-Gasselin, B, Houllier, A-M, Verrier, P, Beaune, P, Loriot, M-A, Siguret, V
• Format: Journal Article
• Language: English
• Published: United States 01.01.2010
• Subjects: Age Factors; Aged; Aged, 80 and over; Aryl Hydrocarbon Hydroxylases - genetics; Cohort Studies; Cytochrome P-450 CYP2C9; Cytochrome P-450 Enzyme System - genetics; Cytochrome P450 Family 4; Dose-Response Relationship, Drug; Epoxide Hydrolases - genetics; Female; Frail Elderly; Genetic Testing; Genetic Variation - drug effects; Genetic Variation - genetics; Hospitalization - trends; Humans; International Normalized Ratio - trends; Male; Mixed Function Oxygenases - genetics; Polymorphism, Genetic - genetics; Prospective Studies; Risk Factors; Vitamin K Epoxide Reductases; Warfarin - pharmacology
• ISSN: 1532-6535
• DOI: 10.1038/clpt.2009.178

Determining the optimal dose of warfarin for frail elderly patients is a challenging task because of the low dose requirements in such patients, the wide interindividual variability of response, and the associated risk of bleeding. The objective of this study was to address the influence of 13 common variations in eight genes on the maintenance dose of warfarin in a cohort of frail elderly inpatients. For our study, we enrolled 300 Caucasian subjects who were hospital inpatients, with a mean age of 86.7 +/- 6 years. In addition to age, genetic variants of VKORC1, CYP2C9, CYP4F2, and EPHX1 were found to be significant predictor variables for the maintenance dose of warfarin, explaining 26.6% of dose variability. Among 132 patients in whom warfarin therapy was initiated with the same low-dose regimen, we studied the relative influences of genetic and nongenetic factors. The time to first international normalized ratio (INR) > or =2 was influenced by VKORC1 and CYP2C9 genotypes (P = 0.0003 and P = 0.0016, respectively); individuals with multiple variant alleles were at highest risk for overanticoagulation (INR >4) (odds ratio, 12.8; 95% confidence interval, 2.73-60.0). In this special population of frail elderly patients with multiple comorbidities and polypharmacy, we demonstrated the main impact of genetic factors on warfarin response.