Which statement correctly describes aspirin's mechanism of action?

Which statement correctly describes aspirin's mechanism of action?

• A. Inactivating cyclooxygenase which blocks thromboxane A2
• B. Antagonizes platelet P2Y12 receptors
• C. Inhibits GPIb receptor binding
• D. Inhibits fibrinogen binding to GPIIb/IIIa

Answer: (A)

Aspirin works by irreversibly inhibiting cyclooxygenase-1 in platelets, which blocks the production of thromboxane A2, a powerful promoter of platelet activation and aggregation. Because platelets lack nuclei, they cannot synthesize new COX-1, so the effect lasts for the platelet’s lifetime, giving an lasting antiplatelet effect at low doses. The other mechanisms described belong to different drugs: blocking the ADP receptor (P2Y12) interferes with ADP signaling rather than COX-1; inhibiting GPIb would affect von Willebrand factor binding; and preventing fibrinogen from binding to GPIIb/IIIa targets later steps of aggregation, not the COX-1–thromboxane pathway that aspirin acts on.

Aspirin works by irreversibly inhibiting cyclooxygenase-1 in platelets, which blocks the production of thromboxane A2, a powerful promoter of platelet activation and aggregation. Because platelets lack nuclei, they cannot synthesize new COX-1, so the effect lasts for the platelet’s lifetime, giving an lasting antiplatelet effect at low doses. The other mechanisms described belong to different drugs: blocking the ADP receptor (P2Y12) interferes with ADP signaling rather than COX-1; inhibiting GPIb would affect von Willebrand factor binding; and preventing fibrinogen from binding to GPIIb/IIIa targets later steps of aggregation, not the COX-1–thromboxane pathway that aspirin acts on.