Pharm 101: Vitamin K

Class

Vitamin

Pharmacodynamics

• 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

• Buttner R. Pharm 101: Warfarin. LITFL

References

• Katzung BG. Basic and Clinical Pharmacology. 14e. 2018: 620-621