Phytonadione Therapy in a Multiple-Drug Overdose Involving Warfarin

Duane Bates, B.Sc.(Pharm.), and Marcy Mintz, M.D.


Pharmacotherapy. 2000;20(10) 

In This Article


Our patient had a prolonged elevation of her INR for 10 days despite daily subcutaneous injections of vitamin K. Due to the vitamin's short half-life, she could have received 10 mg orally or subcutaneously every 8 hours initially and her INR may have been within the normal range within 6 days. However, the prolonged INR may have been due to coingestion of warfarin and acetaminophen and to administration of antibiotics during hospitalization. No published randomized, placebo-controlled studies have evaluated the warfarin-acetaminophen interaction. In our patient, acetaminophen may have contributed to decreased metabolism of warfarin, thereby reducing its clearance.


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