Warfarin and Superwarfarin Toxicity Clinical Presentation

  • Author: Kent R Olson, MD, FACEP; Chief Editor: Asim Tarabar, MD   more...
 
Updated: Feb 7, 2012
 

History

Bleeding is the only expected symptom of significance. Internal bleeding may present with a vast array of symptoms or be occult.

Obtain an accurate history of the amount of warfarin or superwarfarin ingested, when it was ingested, and over what period it was ingested. Additionally, inquire about the circumstances of the ingestion to determine the patient's disposition. If the ingestion was suicidal or surreptitious in nature, the history may be difficult to obtain or the patient or caregiver may give misleading information.

An accurate medication list is important because many drugs increase or decrease the metabolism of warfarin.

The toxic dose of warfarin is highly variable. Generally, a single ingestion of warfarin (10-20 mg) does not cause serious intoxication. In contrast, chronic or repeated ingestion of even small amounts of warfarin (2-5 mg/day) eventually can lead to significant anticoagulation, especially in the presence of interacting drugs. Patients with hepatic dysfunction, malnutrition, or a bleeding diathesis are at the greatest risk of toxicity from warfarin use.

Superwarfarins are extremely potent and can produce prolonged effects even after a small ingestion; as little as 1 mg in an adult can cause coagulopathy.

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Physical Examination

Do not expect to see physical evidence of bleeding after an acute ingestion for at least 24 hours. Life-threatening complications include massive GI bleeding and intracranial hemorrhage. More common findings of excessive anticoagulation are ecchymoses, subconjunctival hemorrhage, epistaxis, vaginal bleeding, bleeding gums, or hematuria.

In all patients, if prolongation of the PT is observed after an acute ingestion, it may appear in as early as 8-12 hours; however, peak effects commonly are delayed until at least 1-2 days postingestion.

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Contributor Information and Disclosures
Author

Kent R Olson, MD, FACEP  Clinical Professor of Medicine and Pharmacy, University of California, San Francisco, School of Medicine; Medical Director, San Francisco Division, California Poison Control System

Kent R Olson, MD, FACEP is a member of the following medical societies: American Academy of Clinical Toxicology and American College of Medical Toxicology

Disclosure: Nothing to disclose.

Coauthor(s)

David N Trickey, MD  Staff Physician, Department of Emergency Medicine, Martin Army Community Hospital

David N Trickey, MD is a member of the following medical societies: American Academy of Emergency Medicine and American College of Emergency Physicians

Disclosure: Nothing to disclose.

Michael A Miller, MD  Assistant Chief, Department of Emergency Medicine, Tripler Army Medical Center; Medical Toxicologist, Tripler Army Medical Center and Central Texas Poison Center, Scott and White Memorial Hospital

Michael A Miller, MD is a member of the following medical societies: American Academy of Emergency Medicine, American College of Emergency Physicians, and American College of Medical Toxicology

Disclosure: Nothing to disclose.

Lisa M Yungmann Hile, MD  Consulting Staff, Medical Director of Emergency Medicine Physician Assistant Fellowship Program, Department of Emergency Medicine, Darnall Army Medical Center

Disclosure: Nothing to disclose.

Derrick Lung, MD, MPH  Fellow, Medical Toxicology, University of California, San Francisco, School of Medicine; Clinical Instructor, Division of Emergency Medicine, Stanford University Medical Center

Derrick Lung, MD, MPH is a member of the following medical societies: American Academy of Clinical Toxicology, American College of Emergency Physicians, American College of Medical Toxicology, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

Asim Tarabar, MD  Assistant Professor, Director, Medical Toxicology, Department of Emergency Medicine, Yale University School of Medicine; Consulting Staff, Department of Emergency Medicine, Yale-New Haven Hospital

Disclosure: Nothing to disclose.

Additional Contributors

John G Benitez, MD, MPH Associate Professor, Department of Medicine, Medical Toxicology, Vanderbilt University Medical Center; Managing Director, Tennessee Poison Center

John G Benitez, MD, MPH is a member of the following medical societies: American Academy of Clinical Toxicology, American Academy of Emergency Medicine, American College of Medical Toxicology, American College of Preventive Medicine, Society for Academic Emergency Medicine, Undersea and Hyperbaric Medical Society, and Wilderness Medical Society

Disclosure: Nothing to disclose.

David A Peak, MD Assistant Residency Director of Harvard Affiliated Emergency Medicine Residency, Attending Physician, Massachusetts General Hospital; Consulting Staff, Department of Hyperbaric Medicine, Massachusetts Eye and Ear Infirmary

David A Peak, MD is a member of the following medical societies: American College of Emergency Physicians, American Medical Association, Society for Academic Emergency Medicine, and Undersea and Hyperbaric Medical Society

Disclosure: Nothing to disclose.

John T VanDeVoort, PharmD Regional Director of Pharmacy, Sacred Heart and St Joseph's Hospitals

John T VanDeVoort, PharmD is a member of the following medical societies: American Society of Health-System Pharmacists

Disclosure: Nothing to disclose.

References

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