Vitamin K Dosing to Reverse Warfarin Based on INR, Route of Administration, and Home Warfarin Dose in the Acute/Critical Care Setting

• Published in: The Annals of pharmacotherapy 2012-12, Vol.46 (12), p.1617-1626
• Main Authors: Tsu, Laura V, Dienes, J Erin, Dager, William E
• Format: Article
• Language: English
• Subjects: Administration, Intravenous; Administration, Oral; Aged; Aged, 80 and over; Anticoagulants - administration & dosage; Anticoagulants - adverse effects; Anticoagulants - antagonists & inhibitors; Antifibrinolytic Agents - administration & dosage; Antifibrinolytic Agents - therapeutic use; Biological and medical sciences; Cohort Studies; Critical Care; Dose-Response Relationship, Drug; Female; Home Care Services; Humans; International Normalized Ratio; Male; Medical sciences; Middle Aged; Pharmacology. Drug treatments; Plasma; Retrospective Studies; Time Factors; Vitamin K - administration & dosage; Vitamin K - therapeutic use; Warfarin - administration & dosage; Warfarin - adverse effects; Warfarin - antagonists & inhibitors
• ISSN: 1060-0280; 1542-6270
• DOI: 10.1345/aph.1R497

Background: Vitamin K is commonly used for reversal of anticoagulation of warfarin. However, the optimal dose and route of vitamin K that does not increase the duration of bridging therapy is unknown. Objective: To determine factors influencing the extent and rate of INR reversal with vitamin K in the acute/critical care setting. Methods: This was a chart review of 400 patients who received vitamin K for reversal of warfarin effects between February 2008 and November 2010. Data collected included international normalized ratios (INRs) 12 hours, 24 hours, and 48 hours prior to vitamin K administration; intravenous or oral vitamin K dose; and whether or not fresh frozen plasma (FFP) was administered. Results: Intravenous vitamin K reduced INR more rapidly than oral vitamin K (5.09, 1.91, 1.54, and 1.41 vs 5.67, 2.90, 2.14, and 1.58) at baseline, 12, 24, and 48 hours, respectively. The dose of vitamin K (p < 0.001), route of administration (p < 0.001), and baseline INR (p < 0.001) influenced subsequent INR values. The INR reduction was similar for intravenous vitamin K doses 2 mg or greater. Home warfarin dose did not affect INR responses to intravenous (p = 0.27) or oral vitamin K (p = 0.98). FFP did not influence INR values at 48 hours. Although longer anticoagulation bridge therapy seemed to be associated with higher vitamin K doses, the incidence (p = 0.63) and duration (p = 0.61) were not significant. Conclusions: Vitamin K dose, route, and initial INR influence subsequent INR values. INR reduction is similar for intravenous vitamin K doses of 2 mg or greater. Preadministration of FFP does not alter INR values at 48 hours or more after vitamin K administration.