Copyright 1998 American Medical Association. All Rights Reserved. Applicable FARS/DFARS Restrictions Apply to Government Use.1998
To the Editor.—The article by Dr Hylek and colleagues1 was an important contribution about the drug interactions of warfarin with acetaminophen and other agents. The authors mention dietary sources of vitamin K as a meaningful antagonist to warfarin resulting in a lower prothrombin time or INR. But they apparently did not ask the patients about consumption of dietary supplements, such as vitamins and multivitamin combinations. Several studies suggest that about 50% of the adult white population take a dietary supplement.2,3 Vitamin K can be purchased in health food stores and is present in some multivitamins.
Eliason BC, Larson W. Acetaminophen and Risk Factors for Excess Anticoagulation With Warfarin. JAMA. 1998;280(8):695-697. doi:10-1001/pubs.JAMA-ISSN-0098-7484-280-8-jbk0826