Can I give vitamin K (Vitamin K) to a patient with elevated International Normalized Ratio (INR) due to warfarin (Warfarin) therapy?

Management of Elevated INR in Patients on Warfarin Therapy

For patients with elevated INR (4.5-10) due to warfarin therapy without evidence of bleeding, vitamin K administration is not routinely recommended as it does not improve patient-important outcomes compared to simply withholding warfarin. 1

INR Management Strategy Based on INR Level

INR 4.5-10 Without Bleeding

• Withhold warfarin doses without routine vitamin K administration 1
• Resume warfarin at a lower dose when INR approaches therapeutic range 1
• Although vitamin K shortens time to normal INR, pooled analysis shows no benefit for major clinical outcomes (bleeding, thromboembolism, mortality) 1
• Risk of major bleeding was similar in patients receiving vitamin K vs. placebo (2% vs. 0.8%) over 1-3 months follow-up 1

INR >10 Without Bleeding

• Consider oral vitamin K 2.5-5 mg 1
• A prospective case series showed 2.5 mg oral vitamin K resulted in low rate of major bleeding by 90 days (3.9%) 1
• Patients given oral vitamin K 2 mg were less likely to have INR >5 by day 3 compared to those with only warfarin held (11.1% vs. 46.7%) 1

INR >10 With Bleeding or Need for Urgent Reversal

• For serious bleeding: administer 10 mg vitamin K by slow IV infusion, supplemented with fresh plasma or prothrombin complex concentrate 1, 2
• For life-threatening bleeding: use prothrombin complex concentrate plus 10 mg IV vitamin K 1

Route of Administration Considerations

• Oral vitamin K is preferred for non-urgent reversal due to safety profile 3

  • Dose of 1-2.5 mg reduces INR from 5.0-9.0 to 2.0-5.0 within 24-48 hours 3
  • For INR >10, a dose of 5 mg may be more appropriate 3

• IV vitamin K achieves more rapid reversal than oral administration 4, 5

  • 44% of IV vitamin K group achieved INR ≤2 within 12 hours vs. 14% for oral route 4
  • IV doses ≥2 mg produce similar INR reduction 5
  • Reserve IV route for urgent reversal due to risk of anaphylactoid reactions 1, 3

Clinical Considerations and Pitfalls

• Risk of bleeding increases significantly when INR exceeds 4.5 1
• Bleeding risk increases logarithmically from 2 per 100 patient-years at INR 2.5-4.9 to 75 per 100 patient-years at INR 6.5 1
• Each 1-point increase in INR approximately doubles risk of intracerebral bleeding 1
• High-dose vitamin K (10 mg) may lead to warfarin resistance for up to a week 1
• Overcorrection of INR can increase thromboembolism risk similar to the bleeding risk of over-anticoagulation 3
• Patient characteristics affecting bleeding risk include advanced age, hypertension, history of stroke, and concomitant medications 1, 3

Monitoring After Intervention

• Monitor INR closely after vitamin K administration 1
• Additional doses of vitamin K may be necessary if INR remains elevated 1
• When resuming warfarin after high-dose vitamin K, consider bridging with heparin until effects of vitamin K have been reversed 1