Abstract

BACKGROUND:

Despite earlier acceptance of oral vitamin K1 (phytonadione) for the treatment of excessive anticoagulation, some recent guidelines do not recommend its use.

OBJECTIVE:

To reevaluate the efficacy of oral vitamin K1 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 K1, 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 photooptical coagulometer.

RESULTS:

In 68 of 71 patients (96%), oral vitamin K1 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 K1 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.