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Pharmacology · single question

What is the MOA of aspirin?

  1. Reversible COX inhibition only
  2. Irreversible inhibition of COX-1/COX-2 via acetylation, reducing thromboxane A2 (antiplatelet effect at low dose) and prostaglandins
  3. Vitamin K antagonism
  4. Phosphodiesterase-3 inhibition
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Correct answer: B. Irreversible inhibition of COX-1/COX-2 via acetylation, reducing thromboxane A2 (antiplatelet effect at low dose) and prostaglandins

Aspirin irreversibly acetylates and inhibits cyclooxygenase. Because platelets cannot synthesize new COX enzyme (they lack a nucleus), even low-dose aspirin permanently suppresses thromboxane A2 production for the platelet's ~7-10 day lifespan, producing its durable antiplatelet effect.

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