The invention provides methods of treating or preventing bleeding events or over-anticoagulation in a subject in need thereof who is identified as having sensitivity to a
vitamin K
antagonist such as
warfarin by administering to the subject a therapeutically effective amount of an FXa inhibitor, which can be a direct or indirect FXa inhibitor, or a
warfarin or VKA alternative
drug or compound. The direct FXa inhibitor can be the
small molecule edoxaban p-toluenesulfonate monohydrate,
edoxaban, or a pharmaceutically acceptable salt and / or
hydrate thereof. In aspects, the subject is identified as having one or more genetic polymorphisms in genes CYP2C9 and / or VKORC1 resulting in loss of function, reduction in function, or aberrant function of these genes and / or their
protein products, and sensitivity to
warfarin. The invention provides methods of administering an FXa inhibitor or warfarin alternative to safely and effectively reduce, prevent, reduce the risk of, prevent the recurrence of, or prevent the risk of recurrence of, conditions such as
embolism,
thrombosis, thromboembolism, etc. in a subject who is in need of
anticoagulant therapy and who is identified as having one or more genetic polymorphisms resulting in warfarin sensitivity.