Is it safe to administer vitamin K2 (menaquinone) 2 mg for 3 days to a patient, considering their medical history and current health status, including potential cardiovascular disease, renal impairment, or anticoagulant therapy?

Vitamin K2 2 mg for 3 Days: Safety and Clinical Considerations

Vitamin K2 (menaquinone) 2 mg daily for 3 days is safe for general supplementation purposes, but this dose and duration are NOT appropriate for reversing warfarin anticoagulation or treating elevated INR. The provided evidence addresses vitamin K1 (phytonadione) for anticoagulation reversal, not vitamin K2 supplementation 1, 2.

Critical Distinction Between Vitamin K Forms

• Vitamin K1 (phytonadione) is the form used for reversing vitamin K antagonist (VKA) anticoagulation and treating elevated INR, with established dosing protocols ranging from 1-10 mg depending on clinical scenario 3, 1, 2
• Vitamin K2 (menaquinone) is primarily used for bone health and cardiovascular calcification prevention, with typical supplementation doses of 2 mL daily per FDA labeling 4
• These are distinct compounds with different clinical applications—vitamin K2 does NOT effectively reverse warfarin anticoagulation 5

Safety Profile for Vitamin K2 Supplementation

• Vitamin K1 and vitamin K2 are not associated with toxicity at therapeutic doses 3
• The FDA-approved dosing for vitamin K2 supplementation is 2 mL (approximately 2 mg) daily, which can be taken continuously 4
• A 3-day course of 2 mg vitamin K2 falls well within safe supplementation parameters 4

Critical Contraindications and Warnings

For patients on warfarin or other vitamin K antagonists:

• High-dose vitamin K2 (145 mg/kg in animal studies) can reduce warfarin's antithrombotic effect, though lower doses (1.5-14 mg/kg) did not significantly interfere 6
• The 2 mg dose is far below the threshold shown to interfere with anticoagulation in research studies 6
• However, patients on VKAs should maintain consistent vitamin K intake to avoid INR fluctuations 3

For patients with renal impairment:

• Patients with advanced chronic kidney disease are particularly vitamin K deficient and may benefit from supplementation 5
• However, vitamin K2 supplementation has not demonstrated cardiovascular benefits in randomized trials of patients with advanced chronic kidney disease despite biochemical improvements 5

Important Clinical Caveats

• If the intent is INR reversal: Use vitamin K1 (phytonadione), not vitamin K2, with doses of 1-10 mg depending on INR level and bleeding status 3, 1, 2
• Route matters for anticoagulation reversal: Oral vitamin K1 is preferred for non-emergency situations, while IV administration (5-10 mg by slow infusion) is reserved for major bleeding 3, 1
• Anaphylaxis risk: IV vitamin K1 carries a risk of anaphylactoid reactions (3 per 100,000 doses), though this does not apply to oral vitamin K2 supplementation 1

Monitoring Recommendations

• For patients on anticoagulation therapy receiving any form of vitamin K supplementation, INR should be monitored within 24-48 hours to assess for interactions 3, 1
• Patients with malabsorption syndromes may have impaired absorption of oral vitamin K formulations and require alternative routes if therapeutic reversal is needed 7