Vitamin K and Warfarin Interaction

Clinical Management of Elevated INR

For patients with INR between 4.5 and 10 without bleeding, the American College of Chest Physicians suggests against routine use of vitamin K, as simply holding warfarin doses is often sufficient 2
If the patient has increased bleeding risk factors, omit the next warfarin dose and consider administering 1-2.5 mg oral vitamin K, as recommended by the American College of Cardiology 3
Randomized trials show that vitamin K administration lowers INR more rapidly than simply holding warfarin, but has not demonstrated reduction in major bleeding events, according to the American College of Chest Physicians 2
For INR >10 without bleeding, administer 3-5 mg oral vitamin K, which will typically lower INR within 24-48 hours, as suggested by the American College of Cardiology 4
For serious bleeding with elevated INR, administer 5-10 mg vitamin K by slow intravenous infusion, as recommended by the American College of Cardiology 5
For life-threatening bleeding, use 4-factor prothrombin complex concentrate (PCC) as first-line therapy plus 10 mg intravenous vitamin K, according to the American College of Cardiology 7

High doses of vitamin K1 may lower INR more than necessary and lead to warfarin resistance for up to a week, as noted by the American College of Cardiology 5
If warfarin is to be resumed after administration of high doses of vitamin K, bridging with heparin may be necessary until the patient becomes responsive to warfarin again, as recommended by the American College of Cardiology 4
Patient-specific factors increasing bleeding risk include age >65 years, history of stroke or GI bleeding, renal insufficiency, anemia, and concomitant use of drugs affecting platelet function, according to the American College of Cardiology 3