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Pharmacology · single question

Aspirin's mechanism of action is:

  1. Selective COX-2 inhibitor
  2. Reversible non-selective COX inhibitor
  3. Phospholipase A2 inhibitor
  4. Irreversible non-selective COX inhibitor
Show answer and explanation

Correct answer: D. Irreversible non-selective COX inhibitor

  • A. Incorrect. SELECTIVE COX-2 inhibition is the MOA of celecoxib (Celebrex) — not aspirin.
  • B. Incorrect. Most NSAIDs (ibuprofen, naproxen) are REVERSIBLE, non-selective COX inhibitors. Aspirin is unique in being irreversible.
  • C. Incorrect. Phospholipase A2 inhibition is the MOA of corticosteroids (via lipocortin/annexin) — not aspirin.
  • D. Correct. Aspirin IRREVERSIBLY inhibits both COX-1 AND COX-2 by acetylating the enzyme active site. Because platelets cannot synthesize new protein, the antiplatelet effect lasts the ENTIRE PLATELET LIFESPAN (7–10 days). This irreversible non-selective COX inhibition is what makes aspirin unique among NSAIDs.

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