Study objective: To compare withholding warfarin therapy with low-dose (2.5 mg) oral vitamin K therapy in excessively anticoagulated patients without bleeding complications.
Design: Prospective and retrospective studies.
Setting: Anticoagulation clinic at a Veterans Affairs institution.
Patients: Twenty-eight men were matched according to initial international normalized ratio (INR) and INR goal ranges.
Interventions: The retrospective arm of the study consisted of chart reviews of overanticoagulated patients whose warfarin doses were held until therapeutic INR values were reached. The prospective arm included overanticoagulated patients who were administered a single 2.5-mg dose of oral vitamin K.
Measurements and main results: Mean days to therapeutic INR values were 2.3+/-0.6 and 1.4+/-0.6 (p=0.001), and mean reduction in INR 1 day after treatment intervention was 1.32+/-0.79 and 3.46+/-1.31 (p<001) U for the withholding and vitamin K groups, respectively.
Conclusion: Compared with withholding the warfarin dose, administration of 2.5 mg of oral vitamin K to excessively anticoagulated patients receiving warfarin significantly reduced the time required to reach a therapeutic INR as well as final INR.