What is the dosing frequency of vitamin K (Vitamin K) for a patient with prolonged prothrombin time (PT) and elevated international normalized ratio (INR)?

Vitamin K Dosing for Prolonged PT and INR

For patients with prolonged PT and INR, vitamin K administration frequency should be determined by the INR level, with a single dose of oral vitamin K (1-2.5 mg) recommended for INRs >10 without bleeding, while for INRs between 4.5-10 without bleeding, vitamin K is not routinely recommended. 1, 2

INR-Based Dosing Algorithm

INR 4.5-10 without bleeding:

• Withhold vitamin K antagonist (VKA) therapy until INR returns to therapeutic range 1
• Avoid routine use of vitamin K as it does not provide benefit for patient-important outcomes such as reduction in major bleeding 1
• Pooled analysis of four randomized controlled trials showed similar rates of major bleeding over 1-3 months between patients receiving vitamin K versus placebo (2% vs 0.8%) 1
• Recheck INR within 24-48 hours to ensure appropriate reduction 2

INR >10 without bleeding:

• Administer oral vitamin K 2-2.5 mg as a single dose 1, 2
• This approach has been shown to reduce the risk of having an INR >5 by day 3 (11.1% vs 46.7% compared to simply withholding warfarin) 1
• A prospective case series demonstrated that 2.5 mg oral vitamin K resulted in a low rate of major bleeding (3.9%) by 90 days in patients with INR >10 1
• Recheck INR within 24 hours to assess response 2, 3

For patients with active bleeding (regardless of INR):

• More aggressive reversal is needed with higher doses of vitamin K (5-10 mg) administered by slow IV infusion 2, 4
• IV vitamin K reduces INR more rapidly than oral vitamin K (reaching levels of 1.91 vs 2.90 at 12 hours) 3
• For life-threatening bleeding, consider prothrombin complex concentrate in addition to vitamin K 2

Monitoring After Vitamin K Administration

• Recheck INR within 24-48 hours after intervention 2
• For IV vitamin K, INR reduction is similar for doses of 2 mg or greater 3
• When warfarin is resumed, reduce the dose by approximately 10-15% from the previous weekly total dose 2
• More frequent monitoring is indicated until stability is re-established 2

Important Considerations and Pitfalls

• Avoid high doses of vitamin K (e.g., 10 mg) for non-emergency reversal as they may lead to warfarin resistance for up to a week 2
• The route of administration significantly impacts the rate of INR reduction - IV administration works faster than oral (5.09 to 1.91 at 12 hours vs 5.67 to 2.90) 3
• For patients with mechanical heart valves, carefully weigh the risk of thromboembolism against the risk of bleeding when deciding on vitamin K dosing 2
• Individualized vitamin K dosing based on index INR and body surface area has been shown to be more effective than fixed-dose regimens (68.9% vs 52.8% return to target INR) 5
• Vitamin K administration for INR correction in patients with coagulopathy due to liver disease has not been associated with lower odds of new bleeding events 6

Special Populations

• For pediatric patients with INR >10 without bleeding, VKAs should be reversed with oral vitamin K 1
• Elderly patients (>65 years) have a higher bleeding risk at any given INR level and may require more cautious management 2
• For patients requiring surgery (e.g., hip fracture), a single 1 mg IV dose of vitamin K can significantly reduce the time for INR reversal and pre-operative delay 7