What is the recommended dose of vitamin K (Vit K) to reverse warfarin (coumarin) anticoagulation?

Vitamin K Dosing for Warfarin Reversal

The recommended dose of vitamin K to reverse warfarin anticoagulation depends on the INR level and clinical scenario, ranging from 1-2.5 mg orally for mildly elevated INR (5-9) without bleeding to 5-10 mg intravenously for serious bleeding. 1, 2

Dosing Based on Clinical Scenario

Non-Bleeding Patient with Elevated INR

• For INR between 5.0 and 9.0 without bleeding:

  • Withhold warfarin and administer 1.0-2.5 mg of vitamin K orally 3, 1
  • This typically lowers INR within 24-48 hours 3
  • For patients at higher risk of bleeding, consider oral vitamin K even for INR values between 4.5-5.0 3, 1

• For INR >10 without bleeding:

  • Administer 3-5 mg oral vitamin K 1, 4
  • A study of 107 patients with INR >10 found that 2.5 mg oral vitamin K resulted in low rates of major bleeding (3.7% at 90 days) 4

Bleeding Patient

• For non-life-threatening bleeding:

  • Administer 2-4 mg vitamin K orally for rapid reversal 3
  • If INR remains high after 24 hours, give additional 1-2 mg orally 3

• For serious bleeding:

  • Administer 5-10 mg vitamin K by slow intravenous infusion (over 30 minutes) 1, 2
  • Intravenous administration produces a more rapid response but carries risk of anaphylactic reactions 3

• For life-threatening bleeding:

  • Administer 10 mg intravenous vitamin K plus 4-factor prothrombin complex concentrate (PCC) 2
  • PCC is preferred over fresh frozen plasma due to faster onset of action (5-15 minutes vs. hours) 3, 2

Route of Administration Considerations

• Oral administration:

  • Preferred for non-urgent reversal due to safety and convenience 3, 5
  • Predictably effective but takes longer to work than IV administration 3
  • Studies show oral vitamin K lowers INR more effectively than simply withholding warfarin 6

• Intravenous administration:

  • More rapid INR reduction compared to oral route (44% vs 14% achieving INR ≤2 within 12 hours) 7
  • Should be administered by slow infusion over 30 minutes to reduce risk of anaphylactic reactions 3, 2
  • Recommended for serious or life-threatening bleeding 2

• Subcutaneous administration:

  • Not recommended due to unpredictable and sometimes delayed response 3, 5

Important Clinical Considerations

• High doses of vitamin K (>10 mg) may lower INR more than necessary and lead to warfarin resistance for up to a week 3, 1

• The dose of vitamin K, route of administration, and baseline INR all significantly influence the rate and extent of INR reversal 8

• For INR values between 2-5 mg, intravenous vitamin K doses of 2 mg or greater produce similar INR reduction 8

• When resuming warfarin after high-dose vitamin K administration, bridging with heparin may be necessary until the patient becomes responsive to warfarin again 1, 9

• Patient-specific factors increasing bleeding risk (age >65, history of stroke/GI bleeding, renal insufficiency, anemia) should be considered when determining vitamin K dosing 1, 2

• For emergency surgery or procedures, the target INR should be <1.5, which typically requires 5-10 mg IV vitamin K plus PCC 2