Phytonadione (Vitamin K1) Dosing for Bleeding
For bleeding due to excessive anticoagulation, the recommended dose of phytonadione (vitamin K1) is 5-10 mg intravenously for significant bleeding, with 10 mg being the standard dose for life-threatening bleeding. 1, 2
Dosing Based on Clinical Scenario
Severe/Life-Threatening Bleeding
- 10 mg of vitamin K1 by slow intravenous infusion (over 30 minutes), administered simultaneously with prothrombin complex concentrate (PCC) 1, 2
- May require additional doses every 12 hours based on INR response 3
- For intravenous administration, maximum effect occurs within 6-12 hours 3
Significant but Non-Life-Threatening Bleeding
- 5-10 mg of vitamin K1 intravenously 2, 4
- Should be administered by slow infusion to reduce risk of anaphylactic reactions 1, 3
Excessive Anticoagulation Without Significant Bleeding
- For INR 4.5-10 without significant bleeding: 1-2.5 mg oral vitamin K 3, 5
- For INR >9 without significant bleeding: 3-5 mg oral vitamin K 3, 5
- Example: For a nonbleeding patient with an INR of 9,2.5 mg phytonadione orally is appropriate 5
Route of Administration Considerations
Intravenous Administration
- Provides more rapid correction of INR than oral route in the first 6-12 hours 6
- At 6 hours, significantly more patients reach therapeutic INR range with IV compared to oral administration 6
- Should be administered by slow infusion over at least 30 minutes to minimize risk of anaphylactic reactions 3, 2
- Anaphylactic reactions occur in approximately 3 per 100,000 doses via a non-IgE mechanism 1
Oral Administration
- By 24 hours, oral and IV routes achieve similar INR correction 6
- Preferred over IV when immediate correction is not required, due to lower risk of anaphylactic reactions 7
- Requires adequate GI absorption; avoid in patients with malabsorption 4
- Bile salts must be given with tablets when endogenous bile supply is deficient 4
Important Clinical Considerations
Monitoring and Follow-up
- INR should be monitored regularly after vitamin K administration 1, 4
- The coagulant effects of phytonadione are not immediate; improvement of INR may take 1-8 hours 4
- For severe bleeding, interim use of blood products (PCC or fresh frozen plasma) is necessary while waiting for vitamin K to take effect 1, 4
Potential Pitfalls
- Doses exceeding 10 mg can prevent re-warfarinization for days and create a prothrombotic state 1, 3
- Phytonadione is not a clotting agent; it works by enabling synthesis of vitamin K-dependent clotting factors 4
- Subcutaneous administration is less effective than IV or oral routes; at 8 hours, mean INR decrease was only 0.4 with SC vs 3.4 with IV administration 8
- In patients with liver disease, repeated large doses may not be effective if initial response is unsatisfactory 4
Special Populations
- In cirrhotic patients, the clinical impact of vitamin K may be limited; a study showed only a 0.3 decrease in INR over 3 days with high-dose IV vitamin K 9
- Elderly patients have higher bleeding risk at any given INR level and may require more cautious dosing 3, 2
Remember that vitamin K will not counteract the anticoagulant action of heparin or direct oral anticoagulants, and is specifically used for vitamin K antagonist reversal 1, 4.