How is chronic warfarin and superwarfarin toxicity treated?

Updated: Jan 19, 2018
  • Author: Kent R Olson, MD, FACEP; Chief Editor: David Vearrier, MD, MPH  more...
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Chronic intoxication resulting from the therapeutic use of warfarin can be evaluated with a careful physical examination and a measurement of the PT and INR.

Chronic ingestions of rodenticide superwarfarin may also be intentional (eg, Munchhausen syndrome) or can occur in the setting of child abuse (Munchhausen by proxy). [17] These patients should be admitted for psychiatric or protective services evaluation.

If the INR is higher than therapeutic levels but less than 5 and the patient is not bleeding, the dose of warfarin may be lowered or the next dose may be omitted. If the patient requires more rapid reversal (eg, elective surgery), administer 1-2.5 mg of vitamin K1 orally with the expectation that the INR will begin to fall within 8 hours, with a maximal effect in about 24 hours.

If the INR is higher than 5 but less than 9 and the patient is not actively bleeding, withhold warfarin for the next 1 or 2 doses, monitor the INR more frequently, and resume therapy at a lower dose when the INR is at the therapeutic level.

Another therapeutic approach would be to withhold 1 dose of warfarin and orally administer vitamin K1, 1-2.5 mg, particularly if the patient is at increased risk of bleeding. For more rapid reversal (eg, urgent surgery), administer vitamin K1, 2.5-5 mg, orally (expected reduction of the INR should occur in about 24 h).

If the INR is higher than 9 and the patient is not bleeding, oral vitamin K1 (2.5 - 5 mg) may be administered with the expectation of a subtstantial reduction in the INR in 24 - 48 hours. In the setting of superwarfarin-induced coagulopathies, daily doses of vitamin K1 in the range of 50-200 mg is recommended.

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