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Pharmacology · single question

A patient on rivaroxaban (Xarelto) — what is the mechanism of action of this medication?

  1. Inhibits vitamin K reductase
  2. Inhibits platelet aggregation via COX-1 blockade
  3. Accelerates antithrombin III to inactivate thrombin
  4. Direct inhibitor of factor Xa (clotting factor)
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Correct answer: D. Direct inhibitor of factor Xa (clotting factor)

  • A. Vitamin K reductase inhibition is the mechanism of warfarin — not rivaroxaban.
  • B. COX-1 inhibition causing antiplatelet effect describes aspirin — not rivaroxaban.
  • C. Accelerating antithrombin III is the mechanism of heparin — not rivaroxaban.
  • D. Correct. Rivaroxaban (Xarelto) is a DIRECT oral anticoagulant — specifically a direct inhibitor of Factor Xa. Unlike warfarin, it does not require monitoring with INR and has predictable pharmacokinetics. It blocks the clotting cascade at Factor Xa.

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