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Another misconception about anticoagulation therapy is that if anticoagulated patients bleed, that risk can be quickly reversed. This is a misconception. The Figure shows data from a trial presented over a decade ago, looking at patients on warfarin for AFib whose INR values were over-elevated. [32] The right-hand side of the Figure shows that an overdose of warfarin could be reversed with intravenous (IV) vitamin K or with oral vitamin K, but only one of the trials resulted in a significant drop in INR values by 4 hours. Most of the trials required 24 hours to achieve a halving of the INR value.
The important point here is that physicians should not think that vitamin K is an instant means of reversing warfarin – and this will be an important consideration in the later discussion of the newer anticoagulation agents. For these it will be possible to use fresh frozen plasma and prothrombin concentrates to provide some of the coagulation factors that are active in reversing the effect of warfarin.
Reiffel JA. Am J Med 2013; 126: 00-00.
[32] Watson HG, Baglin T, Laidlaw SL, Makris M, Preston FE. A comparison of the efficacy and rate of response to oral and intravenous Vitamin K in reversal of over-anticoagulation with warfarin. Br J Haematol. 2001;115:145-149.