Drug of the Week Series - 19.1

General
1

Scenario:
A 58-year-old man with a mechanical heart valve has been taking warfarin regularly. During a routine follow-up, his INR is found to be 5.8. He also reports mild gum bleeding.

Poll:
What is the most likely explanation for this patient’s increased bleeding risk?

  • The drug has increased platelet production.
  • The INR is above the therapeutic range.
  • Warfarin causes direct damage to blood vessels.
  • The drug increases fibrin formation.
0 voters

Question:
Why does warfarin require regular INR monitoring, and what is the significance of vitamin K in its mechanism of action?

MBH/PS

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Warfarin requires regular INR monitoring because its therapeutic window is narrow, and its effect can vary with diet, medications, and liver function.INR monitoring ensures adequate anticoagulation.

Warfarin blocks vitamin K recycling and causes prolonged PT/INR

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Warfarin requires regular INR monitoring to maintain the desired level of anticoagulation and avoid excessive bleeding or clot formation. It works by inhibiting vitamin K recycling, which reduces the production of vitamin K–dependent clotting factors II, VII, IX, and X.

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