CYP2C9 and VKORC1 genotyping for the quality of long-standing warfarin treatment in Russian patients.

A total of 263 warfarin naive patients with indications to long-term anticoagulation were included in prospective multicenter study and randomized into Pharmacogenetics and Standard dosing groups. The loading warfarin dose in Pharmacogenetics group was calculated by Gage algorithm and corrected starting on day 5 of treatment according to INR. In Standard dosing group warfarin initial dose was 5 mg and starting on day 3 of treatment it was titrated according to INR. Pharmacogenetics dosing in comparison with prescription of starting dose of 5 mg decreased major bleedings (0 vs. 6, p = 0.031), time to target INR (11 [9-14] vs. 17 [15-24] days, p = 0.046), and frequency of INR fluctuations ≥4.0 (11% vs. 30.9%, p = 0.002). The advantages of the pharmacogenetics dosing were mainly achieved due to the patients with increased warfarin sensitivity.