Subcutaneous phytonadione for reversal of warfarin-induced elevation of the International Normalized Ratio.

The efficacy and safety of subcutaneous phytonadione in the treatment of patients with asymptomatic excessive International Normalized Ratio (INR) values secondary to warfarin therapy were evaluated. Patients at an outpatient anticoagulation clinic with an INR of 8 or more but less than 14 were given 1 mg of subcutaneous phytonadione, and patients with an INR of 14 or more but less than 20 received 2 mg. The patients were instructed to withhold warfarin therapy for the next 24 hours and to immediately report any bleeding complications. At subsequent visits, patients with an INR of 8 or more but less than 14 were given an additional 1 mg of subcutaneous phytonadione. Patients with an INR above 4.5 were instructed to withhold warfarin therapy for an additional 24 hours. Seventeen patients received the 1-mg dose (group 1), and four patients received the 2mg dose (group 2). In group 1, the mean INR reduction was 49% at 24 hours and 72% at 48 hours and the INR was below 4.5 in 93% of patients at 48 hours. In group 2, the mean INR reduction was 67% at 24 hours and 85% at 48 hours and the INR was below 4.5 in 100% of patients at 48 hours. In four group-1 patients and one group-2 patient, the INR fell below 2.0 at 48 hours. No patients reported hemorrhagic or thrombotic complications. Subcutaneous phytonadione safely lowered excessively high INR values caused by warfarin therapy.