Aspirin Antiplatelet Mechanism — NDEB AFK MCQ
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Correct answer: B — Irreversible acetylation of COX-1, preventing thromboxane A₂ production
Aspirin (acetylsalicylic acid) irreversibly acetylates serine-530 on COX-1 in platelets, permanently blocking the production of thromboxane A₂ (TXA₂, a potent platelet aggregator and vasoconstrictor). Since platelets are anucleate and cannot synthesise new COX, the antiplatelet effect lasts the lifetime of the platelet (7-10 days). This irreversibility distinguishes aspirin from other NSAIDs, which reversibly inhibit COX. Patients on aspirin should NOT discontinue it before dental extractions.
Reference: Katzung – Basic and Clinical Pharmacology, 15th ed., 2021