Successful oral phytonadione (vitamin K) challenge following an infusion-related reaction to intravenous phytonadione.

A woman in her early 60s presented to the emergency room with worsening pain 10 days after an injury to her right abdomen. CT revealed a large subcutaneous haematoma and contained small bowel perforation. She was tachycardic and anaemic and her international normalized ratio (INR) was 2.6 on warfarin for atrial fibrillation. General surgery was consulted and percutaneous drainage of the perforation was recommended, requiring an INR of 1.5 or less. Intravenous (IV) phytonadione was administered to accelerate the lowering of INR; however, the patient developed a severe infusion-related reaction. She recovered once IV phytonadione was stopped and oral diphenhydramine was administered. However, there was still a need for warfarin reversal therapy. A 1.25 mg dose of oral phytonadione was trialled 2.5 hours later and well tolerated. An additional rechallenge of 5 mg by mouth was given without reaction (<8 hours after the initial reaction). Her INR was 1.5 the next morning.