STUDY OBJECTIVES: To study the efficacy and safety of partially correcting therapeutic anticoagulation by administering oral vitamin K1. DESIGN: Prospective interventional trial. SETTING: Outpatient anticoagulation clinic. PATIENTS: Patients who required reversal of their normal or excessive therapy with oral anticoagulant drugs were recruited. INTERVENTIONS: 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.
STUDY OBJECTIVES: To study the efficacy and safety of partially correcting therapeutic anticoagulation by administering oral vitamin K1. DESIGN: Prospective interventional trial. SETTING:Outpatient anticoagulation clinic. PATIENTS: Patients who required reversal of their normal or excessive therapy with oral anticoagulant drugs were recruited. INTERVENTIONS: 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.