What is the recommended dose of vitamin K (phytonadione) for a patient with a mildly elevated International Normalized Ratio (INR)?

From the Guidelines

For a patient with an INR of 1.89, which is only mildly elevated, the recommended dose of vitamin K (phytonadione) is typically not necessary, as this level is close to the therapeutic range and does not significantly increase the risk of bleeding. However, if correction is deemed necessary due to clinical judgment, a low dose of vitamin K, such as 1 mg orally, may be considered to gradually correct the INR without overcorrection, based on the principles outlined in studies such as 1 and 1. The decision to administer vitamin K should be based on the patient's overall clinical condition, including the presence of bleeding or the risk of bleeding, and the specific circumstances that led to the elevated INR. Key considerations include:

• The risk of bleeding increases significantly with INR values above 4, as noted in 1.
• Oral vitamin K is preferred for mild elevations because it provides a gradual correction of the INR, as discussed in 1.
• Higher doses or intravenous administration of vitamin K should be reserved for patients with more significant INR elevations or active bleeding, as these approaches can lead to warfarin resistance, complicating subsequent anticoagulation management, a point emphasized in 1. Monitoring the INR after any intervention is crucial to ensure it returns to the desired therapeutic range. Given the patient's INR is only mildly elevated at 1.89, the primary approach should focus on careful monitoring and adjusting the warfarin dose as necessary, rather than immediate correction with vitamin K, unless there are specific clinical concerns that warrant intervention, as might be guided by the principles in 1 and 1.

From the FDA Drug Label

The recommended dose to correct excessively prolonged prothrombin times caused by oral anticoagulant therapy is, 2.5 mg to 10 mg or up to 25 mg initially. Evaluate INR after 6 to 8 hours, and repeat dose if INR remains prolonged.

The recommended dose of vitamin K (phytonadione) for a patient with a mildly elevated International Normalized Ratio (INR) of 1.89 is 2.5 mg to 10 mg or up to 25 mg initially 2.

• Evaluate the INR after 6 to 8 hours and repeat the dose if the INR remains prolonged.
• The dosage should be kept as low as possible, and prothrombin time should be checked regularly as clinical conditions indicate.

From the Research

Vitamin K Dosing for Mildly Elevated INR

The recommended dose of vitamin K (phytonadione) for a patient with a mildly elevated International Normalized Ratio (INR) of 1.89 is not explicitly stated in the provided studies. However, based on the available evidence:

• For an INR range of 5.0-9.0, a dose of 1-2.5mg of oral phytomenadione (vitamin K(1)) can reduce the INR to 2.0-5.0 within 24-48 hours 3.
• For an INR >10.0, a dose of 5mg may be more appropriate 3.
• Since the patient's INR is 1.89, which is below the range of 5.0-9.0, a lower dose of vitamin K may be considered.
• It is essential to note that the use of vitamin K in patients with warfarin over-anticoagulation lowers excessively elevated INR faster than withholding warfarin alone, but it has not been clearly demonstrated that vitamin K treatment lowers the risk of major hemorrhage 3.

Considerations for Vitamin K Administration

• Oral administration of vitamin K is preferred due to the risk of anaphylactoid reactions with intravenous administration and cutaneous reactions with subcutaneous administration 3.
• The effectiveness of vitamin K in reversing over-anticoagulation may vary depending on the specific anticoagulant used, with vitamin K being less effective for over-anticoagulation after treatment with acenocoumarol or phenprocoumon than after treatment with warfarin 3.