Pharm 101: Vitamin K



  • Confers biologic activity upon factors II (prothrombin), VII, IX and X by participating in their postribosomal modification
  • Two forms:
    • Vitamin K1 is found in food, primarily green leafy vegetables
    • Vitamin K2 synthesised by intestinal bacteria
  • Clinical uses:
    • Reversal of warfarin anticoagulation, prevention of haemorrhagic disease of new born
    • IV or PO Vitamin K1 is available clinically
    • IV administration should be slow as rapid infusion can cause dyspnoea, chest and back pain, and death

Reversal of warfarin anticoagulation
  • Warfarin prevents reductive metabolism of inactive vitamin K to active form so produces biologically inactive VII, IX, X, prothrombin, protein C and S
  • Vitamin K confers biologic activity upon factors II, VII, IX, X by participating in their postribosomal modification
  • Re-establishes normal activity of vitamin K dependent clotting factors II, VII, IX, X
  • 6-24 hours for effect

Further reading


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MBBS (UWA) CCPU Emergency Medicine Trainee with interests in medical education, ECG interpretation, and the use of point-of-care ultrasound in the undifferentiated patient. Co-author of the LITFL ECG Library | Twitter

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