Management of Coumarin/Warfarin Ingestion with Bleeding
For life-threatening bleeding from coumarin ingestion, immediately administer 4-factor prothrombin complex concentrate (PCC) 25-50 U/kg IV plus vitamin K 10 mg by slow IV infusion over 30 minutes, targeting INR <1.5. 1, 2
Immediate Assessment and Stabilization
Determine bleeding severity first—this dictates your reversal strategy:
- Life-threatening bleeding (intracranial hemorrhage, hemodynamic instability, critical site bleeding): Give 4-factor PCC 25-50 U/kg IV immediately PLUS vitamin K 10 mg slow IV infusion over 30 minutes 1, 2
- Major bleeding (non-life-threatening but significant): Administer vitamin K 5-10 mg by slow IV infusion over 30 minutes; consider 4-factor PCC if bleeding is at critical sites or causing hemodynamic instability 1, 2
- Minor bleeding: Temporarily discontinue warfarin and give vitamin K to antagonize effects 3
The key distinction is that life-threatening situations require both immediate factor replacement (PCC) and vitamin K, whereas less severe bleeding may be managed with vitamin K alone 1, 2, 3.
Laboratory Monitoring
Check INR immediately upon presentation and serially thereafter:
- Target INR <1.5 for emergency reversal in life-threatening bleeding 1, 2
- Monitor INR response to guide additional dosing of reversal agents 3
- Fresh frozen plasma is less useful than prothrombin complex concentrates for rapid reversal 3
INR-Based Management Without Active Bleeding
If the patient has elevated INR from coumarin ingestion but no active bleeding, your approach depends on the INR level:
- INR 4.0-5.0: Withhold warfarin and observe; no vitamin K needed unless high bleeding risk factors present 2
- INR 5.0-9.0: Withhold 1-2 doses of warfarin and monitor serial INR; add oral vitamin K 1.0-2.5 mg only if increased bleeding risk factors are present 1, 2
- INR >9.0-10.0: Immediately withhold warfarin and administer oral vitamin K 2.5-5 mg, with INR rechecked within 24 hours 2
Special Considerations for Coumarin Poisoning
Coumarin rodenticides (superwarfarins like bromadiolone, difenacoum) have extremely long half-lives:
- Bromadiolone has an elimination half-life of approximately 140 hours (nearly 6 days) 4
- Difenacoum has a terminal half-life of 11.7 days 5
- These patients may require prolonged treatment with vitamin K (200 mg daily) and frequent Fresh Frozen Plasma administration for months 5
- Plasma concentrations can unexpectedly increase, suggesting enterohepatic recirculation or continued covert ingestion 5
Monitor for covert repeated ingestion: If plasma coumarin concentrations and descarboxyprothrombin levels unexpectedly increase after initial decline, suspect ongoing self-poisoning 5.
Bleeding Risk Factors to Assess
Identify factors that increase bleeding risk and warrant more aggressive reversal:
- Age ≥65 years 1
- History of stroke or gastrointestinal bleeding 1
- Renal insufficiency 1
- Anemia 1
- Concomitant antiplatelet drug use 1
These factors should lower your threshold for administering vitamin K even at lower INR elevations 1, 2.
Common Pitfalls
Avoid fresh frozen plasma as first-line for major bleeding: Prothrombin complex concentrates provide faster and more complete reversal than FFP 3. FFP requires large volumes and takes longer to infuse, delaying hemostasis 3.
Do not use oral vitamin K for emergencies: IV administration (slow infusion over 30 minutes) is required for life-threatening or major bleeding 1, 2. Oral vitamin K is appropriate only for elevated INR without bleeding or minor bleeding 2, 3.
Monitor for prolonged effects with rodenticide poisoning: Unlike pharmaceutical warfarin (half-life 36-42 hours), superwarfarin rodenticides persist for weeks to months and require extended monitoring and treatment 6, 5, 4.