What are the management steps for a warfarin (anticoagulant) overdose?

Management of Warfarin Overdose

For warfarin overdose, immediate management should include discontinuation of warfarin, administration of vitamin K (dose based on INR and bleeding status), and prothrombin complex concentrate (PCC) for life-threatening bleeding. 1, 2

Assessment of Severity

• Evaluate for signs of bleeding:

  • Overt bleeding (blood in stool/urine, melena, petechiae)
  • Excessive bruising or persistent oozing from superficial injuries 2
  • Check INR immediately and monitor every 6 hours initially to catch rapid rises 3

• Categorize severity:

  • Asymptomatic elevated INR without bleeding
  • Minor bleeding (self-limiting)
  • Major/life-threatening bleeding

Management Algorithm Based on Severity

1. Elevated INR Without Bleeding

• INR 4.5-10 without bleeding risk factors:

  • Hold warfarin doses
  • Consider 1-2.5 mg oral vitamin K for patients at increased bleeding risk 1
  • Resume warfarin at lower dose when INR approaches therapeutic range

• INR >10 without bleeding:

  • Hold warfarin
  • Administer 2.5-5 mg oral vitamin K 1
  • Monitor INR within 24 hours
  • Resume warfarin at reduced dose when INR in therapeutic range

2. Minor Bleeding with Elevated INR

• Hold warfarin
• Administer 2.5-5 mg oral vitamin K 4, 1
• Local hemostatic measures
• Recheck INR within 12-24 hours
• Resume warfarin at lower dose once bleeding resolves and INR is therapeutic

3. Major/Life-threatening Bleeding

• Hold warfarin
• Administer 5-10 mg vitamin K via slow IV infusion 4, 1
• Administer 4-factor prothrombin complex concentrate (PCC) at 25 U/kg (preferred over fresh frozen plasma) 4
• For intracranial hemorrhage, target INR <1.4 within 1 hour 1
• Supportive measures:
  • Fluid replacement
  • Red blood cell transfusion if needed
  • Platelet transfusion if thrombocytopenia or platelet dysfunction 4

Important Clinical Considerations

Vitamin K Administration

• Route selection:

  • Oral: Preferred for non-urgent reversal (85% effective within 24 hours) 1
  • IV: For urgent reversal, administer by slow infusion (5-10 mg over 30 minutes) to avoid anaphylactic reactions 1

• Dosing caution:

  • High doses (>10 mg) may cause warfarin resistance for up to a week 1
  • For patients requiring continued anticoagulation, use lower doses (0.5-2.0 mg) to avoid complete reversal 1, 3

Monitoring After Intervention

• Recheck INR within 24 hours after any intervention 1
• Check INR daily until therapeutic range is reached and sustained for 2 consecutive days 1
• Then check 2-3 times weekly for 1-2 weeks 1

Resumption of Warfarin

• For patients requiring continued anticoagulation, resume at a lower dose (10-20% reduction) 1
• Consider thrombotic risk when deciding on timing of resumption:
  • For most patients: Resume after 3-7 days following major bleeding 4
  • For high thrombotic risk patients (mechanical heart valves): Consider earlier resumption with bridging using unfractionated heparin 4

Special Considerations

• Intentional overdose: Classify patients based on pre-existing indications for warfarin (non-therapeutic, moderate risk, high risk for thromboembolic complications) 3

• Superwarfarin (rodenticide) poisoning: May require months of high-dose oral vitamin K therapy due to longer half-life 5

• Thrombotic risk: PCC administration may rarely cause thrombotic complications; monitor closely, especially in patients with history of thrombosis 2, 6

• Warfarin resistance: May persist for up to 2 weeks after high-dose vitamin K administration 3

By following this systematic approach based on severity of bleeding and INR levels, warfarin overdose can be effectively managed to minimize both bleeding and thrombotic complications.