Introduction: Warfarin is a widely used oral anticoagulant with established reversal guidelines in the setting of a supratherapeutic international normalized ratio (INR). Limited literature exists on managing acute warfarin overdoses in patients who are not chronically anticoagulated.
Case: A 15-year-old male, with no indication for anticoagulation, presented to a pediatric emergency department after an acute 1,000 mg warfarin ingestion. He had no significant complaints upon presentation aside from a mild intermittent headache. His past medical history was significant for anxiety, depression, Tourette syndrome, attention deficit hyperactivity disorder, and polysubstance misuse. Computed tomography of his head was unremarkable and serum acetaminophen, salicylate, and ethanol concentrations were negative. Approximately 16 h post-ingestion, his INR was 1.9 with an increase to 3.3 by 26 h. The regional poison center was consulted and recommended, consistent with the CHEST guidelines, holding treatment with vitamin K until INR was >10 or if signs or symptoms of bleeding occurred. The patient was admitted for monitoring and by hospital day (HD) #4, his INR had risen to >11.8 at which point oral vitamin K 10 mg was administered. On HD #7, the patient was deemed stable for transfer to inpatient psychiatry after repeat INRs of 2.9 and 3.4.
Discussion: Case reports have demonstrated early administration of vitamin K can temporarily lower INR and prevent detection of rebound. The CHEST warfarin reversal guidelines describe the risks and benefits with respect to bleeding and thrombosis in the non-intentional overdose patient. Application and extrapolation of these guidelines to acute overdose in patients who lack an indication for anticoagulation may or may not be warranted.
Conclusion: While established clinical guidance exists on reversing a supratherapeutic INR in patients chronically anticoagulated with warfarin, the risks and benefits of extrapolating this approach are unclear in those who lack an indication for anticoagulation.
Keywords: Warfarin; acute overdose; pediatrics; reversal; vitamin K.