Best Tests November 2006
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Oral route first choice for vitamin K in excessive anticoagulation
Thank you to Dr Ian Morison, a haematologist from Dunedin, for drawing our attention to literature on the use of vitamin K that is summarised in a recent meta-analysis1. Oral vitamin K is first choice in treating excessive anticoagulation even when the INR is greater than 10. This is because oral vitamin K is as effective as vitamin K given intravenously and more effective than vitamin K given subcutaneously. Intravenous vitamin K has been associated with anaphylaxis.
The optimal dose of vitamin K has not been determined, but the authors of the meta-analysis recommended that clinicians “should consider administering 1 to 2.5 mg of oral vitamin K in patients receiving warfarin with an INR greater than 6.0 and no clinical considerations preventing its use”.
To administer vitamin K, the intravenous solution should be given orally (the 10 mg tablet is not suitable). Parenteral vitamin K (konakion, 10 mg/mL) is available to general practitioners on a Practitioners’ Supply Order form. It should be stored away from the light; below 25 degrees C.
Patients with major bleeding, of course, need immediate admission.
1. Dezee K, Shimeall T, Douglas K et al. Treatment of Excessive Anticoagulation with phytonadione (Vitamin K): a meta-analysis. Arch Int Med 2006 166 391-7