Correction of excessive anticoagulation with low-dose oral vitamin K-1

Background: Despite earlier acceptance of oral Vitamin K-1 (phytonadione) for the treatment of excessive anticoagulation, some recent guidelines do not recommend its use. Objective: To reevaluate the efficacy of oral vitamin K-1 in correcting excessive anticoagulation. Design: Case series. Setting: Anticoagulation clinics at two university medical centers. Patients: 81 outpatients who had an international normalized ratio (INR) greater than 5.0 but did not have significant bleeding. Interventions: Withholding 1 or 2 doses of warfarin, administering 2.5 mg of oral vitamin K-1, measuring the INR after 24 to 48 hours, and adjusting the warfarin dose. Measurements: INRs were obtained from a portable capillary fingerstick monitor or from an automated photo-optical coagulometer. Results: In 68 of 71 patients (96%), oral vitamin K-1 lowered the INR from between 5.0 and 10.0 to less than 5.0 without inducing resistance to further anticoagulation. Conclusions: Withholding 1 or 2 doses of warfarin and administering 2.5 mg of oral vitamin K-1 is a reliable, safe, and inexpensive way to rapidly correct excessive anticoagulation (INR > 5.0) in patients who do not have serious bleeding episodes and have an INR of less than 10.0.