CYP2C9 gene polymorphisms and warfarin dose requirement: a single-center experience in Turkey

Aim: In this study, we aimed to evaluate the relationship between genetic structure and daily dose requirement in patients under warfarin therapy presenting at our hospital. Materials and methods: A total of 80 patients (45 female and 35 male) aged between 29 and 80 years (mean age: 59.86 ± 14.46 years), using warfarin for at least 1 month and presenting at Atatürk University Medical Faculty Outpatient Clinic between May 2009 and May 2010, were included in the study. Analysis of CYP2C9 1075 A C and CYP2C9 430 C T polymorphisms were performed using polymerase chain reaction (PCR) and the reverse-hybridization method. Results: Patients with CYP2C9 genotype variants *2/*2, *2/*3, and *3/*3 required 3.40 mg/day, which was 1.57 mg less warfarin per day than patients with the wild-type genotype (*1/*1) (4.97 mg/day), and this difference was statistically significant (P = 0.014). Additionally, the patients with *1/*2 and *1/*3 genotypes required 3.93 mg/day, which was 1.04 mg less warfarin per day than those with the wild-type genotype (P = 0.01). Conclusion: Because patients with *2 and *3 variants of the CYP2C9 gene are at a high risk for bleeding while taking an oral anticoagulant, clinicians should start at lower doses of warfarin in these patients and should make strict dose adjustments.