Vitamin K Antagonists
Start with the big picture
VKAs block vitamin K epoxide reductase, reducing activation of clotting factors II, VII, IX, and X as well as proteins C and S. Because existing factors must clear, anticoagulation develops gradually; acute thrombosis may require heparin bridging. Warfarin is monitored with PT/INR, and its effects and dose can be influenced by genetics, interacting medicines, and vitamin K intake. Important risks include bleeding, skin necrosis, and fetal harm, so pregnancy is a contraindication. The topic also introduces reversal with vitamin K and, in severe hemorrhage, additional blood-product-based treatment. Together, these features make monitoring, consistent dietary habits, and careful medication review central to safe VKA therapy.
What you'll learn
- Explain how VKAs alter vitamin K–dependent clotting factors and natural anticoagulants.
- Describe the delayed onset of warfarin and the role of heparin bridging.
- Identify key monitoring, interaction, dietary, and genetic considerations.
- Recognize major adverse effects, contraindications, and reversal approaches.
- Summarize common therapeutic uses and peri-procedural management principles.
Continue your study
Work through the complete notes and reinforce the topic with the study tools available in the full lesson.
