Is oral vitamin K (Vitamin K) available?

Oral Vitamin K Availability

Yes, vitamin K is available in oral form and is used clinically for various indications including anticoagulation reversal and supplementation in deficiency states.

Forms of Oral Vitamin K

• Pharmaceutical-grade phytonadione (vitamin K1) is available as prescription tablets in the United States 1
• Over-the-counter (OTC) vitamin K supplements are also available, though with variable quality and actual vitamin K content 1
• Two main forms exist:
  • Phylloquinone (vitamin K1) - found in green leafy vegetables and used in most pharmaceutical preparations 1, 2
  • Menaquinones (vitamin K2) - available as supplements (particularly MK-7) 2, 3

Clinical Applications

Anticoagulation Management

• Reversal of excessive anticoagulation: Oral vitamin K is used to reverse excessive anticoagulation in patients on vitamin K antagonists (VKAs) like warfarin 1, 4
• Dosing for non-life-threatening bleeding: 1-2 mg orally for non-life-threatening major bleeding 4
• Time to effect: Oral supplementation takes about 24 hours to achieve maximum effect 1
• Comparison to IV administration: IV vitamin K has a faster onset of action (6-12 hours) compared to oral vitamin K (24 hours) 1

Considerations in Anticoagulation Reversal

• The American Society of Hematology guidelines note that oral vitamin K administration might be considered for:
  • Patients at high risk of bleeding complications
  • Situations where INR is expected to be prolonged (e.g., intentional overdose, interacting drugs) 1
• For life-threatening bleeding, IV vitamin K (5-10 mg) plus prothrombin complex concentrate is recommended rather than oral vitamin K 4

Pharmacokinetics

• Both vitamin K1 and MK-7 are well absorbed orally, with peak serum concentrations at 4 hours after intake 2
• MK-7 (vitamin K2) has a much longer half-life than vitamin K1, resulting in:
  • More stable serum levels
  • Accumulation to higher levels (7-8 fold) during prolonged intake 2, 5
• Vitamin K1 and MK-4 remain present in plasma for 8-24 hours, whereas long-chain menaquinones can be detected up to 96 hours after administration 5

Practical Considerations

Cost and Availability Issues

• Pharmaceutical-grade oral vitamin K tablets are expensive in the United States 1
• OTC vitamin K supplements have variable quality and actual vitamin K content:
  • Some OTC brands contain less or more vitamin K than advertised
  • Available OTC tablet strengths would require multiple tablets to achieve recommended therapeutic doses 1

Potential Interactions

• Patients using anti-vitamin K drugs should be monitored with blood clotting tests when taking oral vitamin K 1
• MK-7 supplements providing ≥50 μg/day may interfere with oral anticoagulant treatment in a clinically relevant way 2

Nutritional Sources

• Primary dietary sources of vitamin K1 include leafy greens, cruciferous vegetables, asparagus, prunes, peas, and parsley 1
• Menaquinones (vitamin K2) are synthesized by certain intestinal bacteria and can contribute to overall vitamin K status 6

Oral vitamin K is an important option in clinical practice, particularly for managing anticoagulation and addressing vitamin K deficiency, though considerations around formulation, dosing, and interactions must be carefully evaluated.