Warfarin is the most common form of oral
anticoagulant therapy. Although it has indisputable benefit in the management of thromboembolic disease,
warfarin-associated coagulopathy (WAC) is a well-documented complication of its use. As
warfarin exerts its effect by impairing formation of the
vitamin K-dependent
clotting factors, a cornerstone of WAC management is
vitamin K replacement. Daily
vitamin K supplementation is an emerging approach to regulate international normalized ratios in difficult-to-control patients. Mild WAC without
bleeding can often be managed with
warfarin withdrawal alone. For excessive international normalized ratio elevation in the absence of
bleeding, low-dose oral
vitamin K (1?2.5 mg) is sufficient and achieves the same degree of international normalized ratio correction by 24 h as intravenous
therapy. The stable patient with WAC and minor
bleeding can also be given oral
vitamin K, with correction of the underlying defect. Major
bleeding should first be managed with factor replacement for immediate correction of the coagulopathy, using either a
prothrombin complex concentrate or fresh-frozen plasma. High-dose
vitamin K (10 mg) should be given concurrently via
intravenous infusion to confer lasting correction.
Warfarin resistance and
vitamin K-associated
anaphylaxis are rare. Despite development of new oral
anticoagulant therapy compounds,
warfarin will probably retain a prominent role in
thromboembolism management for several years to come.