Prospective evaluation of anticoagulant reversal with oral vitamin K1 while continuing warfarin therapy unchanged.
OBJECTIVE
To study the efficacy and safety of partially correcting therapeutic anticoagulation by administering oral vitamin K1.


METHODS
Prospective interventional trial.


METHODS
Outpatient anticoagulation clinic.


METHODS
Patients who required reversal of their normal or excessive therapy with oral anticoagulant drugs were recruited.


METHODS
All patients received a single oral dose of vitamin K1. The dose was calculated using a regression formula and was intended to decrease the international normalized ratio (INR) to a predetermined value. Patient follow-up continued for 8 weeks. We compared the actual change of the INR to the predicted change.


RESULTS
Sixty-five reversals of anticoagulant therapy were initiated in the study group. Sixty-four of the 65 reversals were successful. The mean (+/-SEM) initial INR was 2.6+/-0.1 for the preprocedure patients and 8.4+/-0.5 for the excessively anticoagulated patients. The predicted change in the INR correlated with the actual change (r = 0.92, p < 0.0001). There were no thromboembolic events and only one hemorrhagic complication. The mean (+/-SEM) dose of oral vitamin K1 was 5.0+/-0.3 mg for the preprocedure patients and 10.0+/-1.0 mg for the excessively anticoagulated patients.


CONCLUSIONS
The administration of a single oral dose of vitamin K1 is a safe and effective method for partially reversing anticoagulant therapy without disrupting the daily maintenance dose of warfarin. A reliable regression formula was developed to predict the dose of vitamin K1 needed to achieve the desired INR.
Wentzien
T H
TH
Department of Medicine, Santa Clara Valley Medical Center, San Jose, CA, USA.
O'Reilly
R A
RA
Kearns
P J
PJ
D000925:Anticoagulants / Q000627:therapeutic use*; D005260:Female; D006490:Hemostatics / Q000494:pharmacology*; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D014812:Vitamin K / Q000494:pharmacology*; D014859:Warfarin / Q000627:therapeutic use*
D000925:Anticoagulants; D006490:Hemostatics; D014812:Vitamin K; D014859:Warfarin