Switching Study From Warfarin to Rivaroxaban

The study objective is to investigate the pharmacodynamics (effects of a drug product) when switching the treatment from warfarin to rivaroxaban. 84 young, healthy subjects will participate; they will be treated following a randomized, parallel-group (Treatments A, B, and C), placebo-controlled (Treatment B), and single-blind (Treatments A and B) design. The first two groups (A, B) will receive warfarin for approximately one week to adjust their blood coagulation values to a specific level, i.e. to maintain an INR (international normalized ratio) of 2.0 - 3.0. This range is commonly used for long-term anticoagulant treatment. The first group (A) will receive rivaroxaban for four days, the second group (B) will take placebo. On the last day, all subjects in groups A and B will receive vitamin K to neutralize the effects of warfarin. The third group (C) will not undergo prior treatment with warfarin but will receive rivaroxaban for four days.