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Warfarin Overdose in an Adolescent Not Dependent on Anticoagulation: Reversal Strategy and Kinetics

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Abstract

Introduction

Warfarin induces coagulopathy. Guidelines protocolize reversal of supratherapeutic international normalized ratio (INR) in patients dependent on anticoagulation, but practices vary for reversing warfarin-induced coagulopathy after overdose in non-warfarin-dependent patients.

Case Report

This is the report of a 15-year-old female who ingested her father’s warfarin (100–200 mg) in a self-harm attempt. At hour 24 post-ingestion, her INR was 2.00 and she was admitted for monitoring. Reversal of coagulopathy was initially deferred pending the INR trend. The INR was 5.10 at hour 60 and 2.5 mg oral vitamin K1 (VK1) was given. At hour 85, the INR peaked at 6.67 and she received a second oral dose of 2.5 mg VK1. On day 8, she was medically cleared with an INR of 1.31. On day 11, she developed lower abdominal pain and diarrhea. Imaging revealed a duodenal hematoma, and symptoms improved spontaneously. She was again medically cleared 13 days post-ingestion. Her serum warfarin concentration peaked at 19 mcg/mL at hour 46. Serial warfarin concentrations were obtained, demonstrating first-order elimination kinetics and a 30-hour half-life.

Conclusion

A restrictive approach to coagulopathy reversal in non-warfarin-dependent patients with intentional warfarin overdose may result in worsening coagulopathy, bleeding, and lengthy hospital stay. Given the risk for significant, prolonged coagulopathy, these patients should be treated early with VK1, with subsequent serial INR monitoring and probable additional VK1 dosing. Delayed peak warfarin concentrations support consideration of gastrointestinal decontamination in late presenters.

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Acknowledgements

The authors extend their deep gratitude to Dr. Valerie Ward, MD MPH, and Mr. Ethan Bremner of Boston Children’s Hospital’s Department of Radiology for their assistance with the provision and interpretation of the radiographic images found in Fig. 2.

Funding

None.

Author information

Author notes

  1. C. James Watson

    Present address: Department of Emergency Medicine, Maine Medical Center, 22 Bramhall Street, Portland, ME, 04102, USA

Authors and Affiliations

  1. Harvard Medical Toxicology Program, Boston Children’s Hospital, 300 Longwood Avenue, Mailstop 3025, Boston, MA, 02115, USA

    Michael D. Simpson, James D. Whitledge & Michele M. Burns

  2. Department of Emergency Medicine, Brigham and Women’s Hospital, Boston, MA, USA

    Michael D. Simpson

  3. Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA, USA

    James D. Whitledge

  4. Department of Pharmacy, Boston Children’s Hospital, Boston, MA, USA

    Al Patterson

  5. Division of Emergency Medicine, Boston Children’s Hospital, Boston, MA, USA

    Michele M. Burns

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  1. C. James Watson
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Contributions

Study concept and design: CJW, MDS, JDW, MMB.

Acquisition of the data: CJW, MDS, JDW, MMB.

Analysis and interpretation of the data: CJW, MDS, JDW, AP, MMB.

Drafting of the manuscript: CJW.

Critical revision of the manuscript: CJW, MDS, JDW, AP, MMB.

Corresponding author

Correspondence to C. James Watson.

Ethics declarations

Consent for Publication

Consent for publication of this case was obtained and provided to the journal in accordance with JMT policy.

Conflict of Interest

CJW, MDS, JDW, and AP report no conflicts of interest. MMB reports that she is the Pediatric Toxicology Section Editor at UpToDate.

Additional information

Supervising Editor: Andis Graudins, MB BS, PhD

Publisher's Note

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Data in this manuscript were previously presented at the American College of Medical Toxicology (ACMT) Annual Scientific Meeting, Virtual, March 2022.

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Cite this article

Watson, C.J., Simpson, M.D., Whitledge, J.D. et al. Warfarin Overdose in an Adolescent Not Dependent on Anticoagulation: Reversal Strategy and Kinetics. J. Med. Toxicol. 18, 334–339 (2022). https://doi.org/10.1007/s13181-022-00907-1

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  • DOI: https://doi.org/10.1007/s13181-022-00907-1

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