What is the management for a warfarin (anticoagulant) overdose?

Management of Warfarin Overdose

For patients with warfarin overdose, management should include immediate discontinuation of warfarin, assessment of bleeding status, and reversal of anticoagulation based on INR level and presence of bleeding. 1, 2

Assessment and Initial Management

• Determine severity based on:

  • INR level
  • Presence/absence of bleeding
  • Patient's underlying thrombotic risk

• For all patients with suspected warfarin overdose:

  • Immediately discontinue warfarin
  • Check INR promptly (don't delay treatment while waiting for results)
  • Monitor INR daily until decreasing, then every 2-3 days until therapeutic 1

Management Algorithm by Clinical Scenario

1. Asymptomatic Elevated INR (No Bleeding)

• INR < 5.0:

  • Hold 1-2 doses of warfarin
  • No vitamin K administration necessary
  • Resume warfarin at 10-20% reduced weekly dose when INR returns to therapeutic range 1

• INR 5.0-9.0:

  • Hold warfarin doses
  • Consider oral vitamin K 1.0-2.5 mg (especially in patients with increased bleeding risk)
  • Resume warfarin at reduced dose (10-20% lower) when INR returns to therapeutic range 1

• INR > 9.0 without bleeding:

  • Hold warfarin
  • Administer oral vitamin K 1.0-2.5 mg
  • Monitor INR more frequently
  • Resume at reduced dose when therapeutic 1

2. Patients with Active Bleeding or Requiring Emergency Surgery

• For major bleeding or emergency surgery:

  • Four-factor prothrombin complex concentrate (PCC) at dose based on INR:
    • INR 2 to <4: 25 units/kg (maximum 2500 units)
    • INR 4 to 6: 35 units/kg (maximum 3500 units)
    • INR >6: 50 units/kg (maximum 5000 units) 1
  • PLUS intravenous vitamin K (5-25 mg, rarely up to 50 mg for severe hemorrhage) 2
  • Check INR 30-60 minutes after PCC administration (target INR <1.5) 1

• For minor bleeding:

  • Hold warfarin
  • Consider oral vitamin K 1-2.5 mg
  • If bleeding progresses, escalate to management for major bleeding 2

3. Severe Hemorrhage (Life-Threatening)

• Immediate interventions:
  • Four-factor PCC (as above)
  • IV vitamin K 5-25 mg
  • Consider fresh frozen plasma (200-500 mL) or Factor IX complex if PCC unavailable 2
  • Packed red blood cells for significant blood loss 2
  • Monitor for fluid overload, especially in elderly or patients with heart disease 2

Special Considerations

• Thrombotic risk: Patients with mechanical heart valves or recent thrombosis require careful management to avoid complete reversal of anticoagulation and subsequent thrombosis

• Vitamin K administration route:

  • Oral administration is preferred for non-urgent correction (safer than IV)
  • IV administration provides faster correction but carries risk of anaphylactoid reactions
  • Subcutaneous administration is less effective than IV 3

• Warfarin resistance: High doses of vitamin K (>10 mg) may cause warfarin resistance for up to 2 weeks, making it difficult to re-anticoagulate patients 4

• Monitoring after reversal:

  • Check INR frequently (6-hourly initially) to catch rapid rises
  • When resuming warfarin, start at reduced dose (10-20% lower than previous) 1

Pitfalls to Avoid

1. Overcorrection: Excessive vitamin K can cause warfarin resistance and increase thrombotic risk

2. Delayed treatment: Don't wait for INR results before initiating reversal therapy in patients with serious bleeding 5

3. Inappropriate use of blood products: Fresh frozen plasma and Factor IX complex carry risks of viral transmission and thrombosis; use only for severe, life-threatening bleeding 2

4. Inadequate monitoring: Failure to check INR frequently after reversal can miss rebound anticoagulation

5. Neglecting underlying cause: Always investigate and address the cause of warfarin overdose (drug interactions, dosing errors, etc.)

By following this structured approach based on INR level and bleeding status, warfarin overdose can be effectively managed while balancing the risks of hemorrhage and thrombosis.