Impaired Warfarin Response Secondary to High‐Dose Vitamin K1 for Rapid Anticoagulation Reversal: Case Series and Literature Review

The literature suggests that unresponsiveness to warfarin can continue for 1 week or longer after administration of high‐dose vitamin K 1 10 mg or greater; however, there is a lack of supporting data to define the duration and clinical consequences of impaired warfarin response with high doses of vitamin K 1 . This case series describes four patients receiving indefinite warfarin therapy who received high and, in most cases, repeated doses of vitamin K 1 for urgent reversal of therapeutic anticoagulation for an invasive procedure or surgery. The patients displayed impaired warfarin response for 11 days–3.5 weeks after administration of vitamin K 1 10–40 mg. The associated financial burden for the patients was substantial. We reviewed the literature to examine the mechanism of impaired warfarin response, and the clinical efficacy, safety, and appropriateness of vitamin K 1 and fresh‐frozen plasma in urgent reversal of anticoagulation.