Disclosures: Austin M. Boos, DO: No financial relationships or conflicts of interest

Case Diagnosis: A 65-year-old male on warfarin for recurrent ischemic strokes with a sudden change in daily warfarin requirement.

Case Description or Program Description: The patient presented to rehabilitation with severe oropharyngeal dysphagia requiring continuous enteral feeds via g-tube for nutrition. On admission, he was transitioned from continuous to nocturnal feeds scheduled from 4pm until 8am each day. His average daily dose of warfarin at that time was 10mg, which was administered nightly around 7 pm. During his stay, he was transitioned to a more physiologic feeding regimen specifically bolus feeds, given four times daily at 6am, 10am, 6pm and 9pm. Two days after this transition, his INR increased rapidly reaching a peak value of 7.0, requiring prompt administration of vitamin K due to his elevated bleeding risk.

Setting: Acute Inpatient Rehabilitation Hospital

Assessment/Results: After an extensive review of the patient’s medications, which did not reveal any pharmacologic interactions, it was concluded that the transition from nocturnal tube feeds with co-administration of warfarin, to bolus tube feeds without co-administration of warfarin, led to the rapid change in warfarin absorption.

Discussion (relevance): Warfarin is a commonly prescribed anticoagulant which derives its therapeutic effects via the inhibition of vitamin K-dependent clotting factors. The challenges of warfarin dosing, specifically due to its narrow therapeutic window and frequent medication interactions are generally well-recognized by health care providers. Although case reports have been published documenting reduced efficacy of warfarin with co-administered with enteral nutrition formulas, this association can be easily overlooked by providers. This case report highlights the potential consequences of not accounting for enteral dietary inputs when managing warfarin.

Conclusions: Co-administration of enteral tube feeds with warfarin can lead to decreased efficacy. As such, providers should pay particular attention when adjusting aspects of enteral feeds, including: administration times, amount or nutrition content.

Level of Evidence: Level IV

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PM&R Meeting Abstracts - https://pmrjabstracts.org/abstract/an-unexpected-cause-of-supratherapeutic-international-normalized-ratio-a-case-report/