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 K1 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 K1. This case series describes four patients receiving indefinite warfarin therapy who received high and, in most cases, repeated doses of vitamin K1 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 K1 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 K1 and fresh-frozen plasma in urgent reversal of anticoagulation.