Robert C. Pendleton, MD; Sara Vazquez, PharmD, BCPS, CACP
Potential Financial Conflicts of Interest: None disclosed.
Pendleton R., Vazquez S.; Vitamin K to Correct Overanticoagulation. Ann Intern Med. 2009;151:433-434. doi: 10.7326/0003-4819-151-6-200909150-00018
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Published: Ann Intern Med. 2009;151(6):433-434.
TO THE EDITOR:
We read with interest the article by Crowther and colleagues (1) evaluating the efficacy of low-dose oral vitamin K to correct excessive anticoagulation in patients receiving warfarin. First, Crowther and colleagues should be commended for carrying out such an important and well-designed study in an area that has received little attention. Despite warfarin accounting for one of the highest annual rates of adverse drug event–related deaths in the United States, the management of excessive anticoagulation in a clinical practice setting has received little study.
Although Crowther and colleagues could not demonstrate a reduction in bleeding events with oral vitamin K, several important considerations should be mentioned. First, Crowther and colleagues do not discuss the duration of warfarin therapy before the elevated INR was found. This may be important, because the annualized bleeding rate is 2-fold higher in the first month of warfarin therapy (2), and as such, outcomes may be different during the early period of warfarin management. Second, Crowther and colleagues did not mention other potentially important clinical variables that may increase risk for bleeding in the setting of excessive anticoagulation, such as concomitant antiplatelet agents or presence of a structural site prone to bleeding (such as recent surgery) (3). Finally, it is important to recognize that this was mostly a study of vitamin K in patients with a modestly elevated INR: 67% of patients had an INR less than 6.0. Because the overall study was underpowered to detect benefits of low-dose vitamin K in reducing major bleeding events, this could be an even greater issue for patients with an INR greater than 6.0.
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