Is vitamin K recommended in patients on warfarin (coumarin anticoagulant) therapy?

From the Guidelines

Vitamin K is not recommended for routine use in patients on warfarin therapy, but may be considered in specific situations where the INR is elevated and the patient is at high risk of bleeding. The use of vitamin K in patients on warfarin therapy is a complex issue, and the decision to administer it should be made on a case-by-case basis. According to the American Society of Hematology 2018 guidelines for management of venous thromboembolism, the guideline panel conditionally recommends against administering oral vitamin K for patients presenting with INRs between 4.5 and 10.0 1. However, administration of oral vitamin K might be considered for patients at high risk of developing bleeding complications or in situations where the INR is expected to be prolonged for a longer period of time.

Some key points to consider when deciding whether to administer vitamin K to a patient on warfarin therapy include:

• The patient's INR level: If the INR is only slightly elevated, it may be possible to simply withhold warfarin doses and monitor the patient's INR closely 1.
• The patient's risk of bleeding: If the patient is at high risk of bleeding, administration of vitamin K may be necessary to rapidly reverse anticoagulation 1.
• The patient's overall health status: Patients with certain medical conditions, such as liver or kidney disease, may require closer monitoring and more cautious use of vitamin K 1.

In general, low doses of vitamin K (typically 1-2.5 mg orally) may be prescribed to reverse excessive anticoagulation in patients with dangerously elevated INR levels or active bleeding while on warfarin 1. However, the use of vitamin K should always be carefully considered and monitored, as it can counteract the anticoagulant effects of warfarin and increase the risk of blood clots. Patients on warfarin should always consult their healthcare provider before taking any vitamin K supplements or significantly changing their diet, as these changes require careful monitoring and potential warfarin dose adjustments to maintain therapeutic anticoagulation levels.

From the FDA Drug Label

OVERDOSAGE ... Excessive anticoagulation, with or without bleeding, may be controlled by discontinuing warfarin sodium tablets therapy and if necessary, by administration of oral or parenteral vitamin K1. If minor bleeding progresses to major bleeding, give 5 to 25 mg (rarely up to 50 mg) parenteral vitamin K1.

Vitamin K administration is recommended in patients on warfarin therapy who experience excessive anticoagulation, with or without bleeding, as a way to control and reverse the anticoagulant effects of warfarin 2.

From the Research

Vitamin K Recommendation for Patients on Warfarin Therapy

• Vitamin K is recommended for patients on warfarin therapy who have an elevated international normalized ratio (INR) as it can help lower the INR into a safe range, reducing the risk of major bleeding 3, 4, 5.
• The use of vitamin K in patients with warfarin over-anticoagulation can lower excessively elevated INR faster than withholding warfarin alone 3.
• Oral administration of vitamin K is preferred due to the risk of anaphylactoid reactions with intravenous administration and cutaneous reactions with subcutaneous administration 3.
• A dose of 1-2.5mg of oral phytomenadione (vitamin K1) can reduce the INR from 5.0-9.0 to 2.0-5.0 within 24-48 hours, and a dose of 5mg may be more appropriate for an INR >10.0 3, 5.

Factors Affecting Vitamin K Dosage

• Patient characteristics, such as age, body weight, co-morbidity, frailty, warfarin daily dose, and CYP2C9 and VKORC1 polymorphism, can affect the response to vitamin K and the rate and extent of INR reversal 6.
• The source and chemical forms of vitamin K can also influence the INR, with high vitamin K intake decreasing the therapeutic effectiveness of warfarin and poor vitamin K status increasing the sensitivity to small changes in vitamin K intake 7.

Safety and Efficacy of Vitamin K

• The use of vitamin K in patients with warfarin over-anticoagulation has been shown to be safe and effective in reducing the INR, with a low risk of major bleeding and thromboembolism 4, 5.
• However, current dosing algorithms for vitamin K administration may not take into account the variability in response to vitamin K, and a more individualized approach may be needed to improve the safety of warfarin therapy 6.