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Oral vs. IV Vitamin K for Reversing Excessive Anticoagulation

Results from a small randomized trial show that an oral dose is as effective as an intravenous one.

Data from nonrandomized and uncontrolled studies suggest that oral vitamin K works somewhat slower than, but is nearly as effective as, less commonly used IV vitamin K for reversing excessive warfarin anticoagulation. Researchers in Israel randomized 61 patients with excessive anticoagulation (INR range, 6.1-19.4; mean, 9.2), but without major bleeding, to receive IV or oral vitamin K. Patients with moderately high INRs (6-10) received either 0.5 mg intravenously or 2.5 mg orally; patients with very high INRs (>10) received 1 mg or 5 mg, respectively.

Among patients with moderately high baseline INRs, IV vitamin K reversed the excessive anticoagulation more rapidly than did oral vitamin K: At 4 hours, mean INRs were approximately 5 with IV vitamin K and 7 with oral. Mean INRs in both the IV and oral groups fell to 2.6-2.9 at 24 hours. Among patients with very high baseline INRs, levels fell at roughly the same rate in the IV and oral groups, to a mean of about 3 at 48 hours. Overall, 4 patients in the IV groups and 2 in the oral groups failed to achieve INRs of <4.0 by 24 hours. No adverse events, including thrombotic events, occurred during the 28-day follow-up.

Comment: These data suggest that oral vitamin K reverses excessive anticoagulation as safely and effectively as IV vitamin K does. Moreover, in a recent randomized trial, oral vitamin K was more effective than subcutaneous vitamin K for reducing moderately elevated INRs in patients without current bleeding (Journal Watch Sep 10 2002).

— Thomas L. Schwenk, MD

Published in Journal Watch General Medicine December 19, 2003

Citation(s):

Lubetsky A et al. Comparison of oral vs intravenous phytonadione (vitamin K₁) in patients with excessive anticoagulation: A prospective randomized controlled study. Arch Intern Med 2003 Nov 10; 163:2469-73.

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