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

The efficacy and safety of subcutaneous phytonadione in the treatment of pa tients with asymptomatic excessive International Normalized Ratio (INR) val ues secondary to warfarin therapy were evaluated. Patient at an outpatient anticoagulation clinic with an INR of 8 or more bu t less than 14 were given 1 mg of subcutaneous phytonadione, and patients w ith 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 immedi ately report any bleeding complications. At subsequent visits, patients wit h an INR of 8 or more but less than 14 were given an additional I mg of sub cutaneous phytonadione. Patients with an INR above 4.5 were instructed to w ithhold warfarin therapy for an additional 24 hours. Seventeen patients received the l-mg dose (group I), and four patients rece ived the 2-mg 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 MR values caused by walfarin therapy.