What is the mechanism of aspirin's antiplatelet effect?

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What is the mechanism of aspirin's antiplatelet effect?

Aspirin’s antiplatelet effect comes from irreversibly inhibiting COX-1 in platelets, which lowers thromboxane A2 production. Thromboxane A2 is a powerful promoter of platelet aggregation and vasoconstriction, so when COX-1 is blocked, platelets become less prone to clump together. The inhibition is irreversible because platelets lack a nucleus and cannot make new COX-1; as a result, the effect lasts for the platelet’s entire lifespan (about 7–10 days). Endothelial cells can synthesize new COX-1 and restore prostacyclin production over time, which helps balance bleeding risk. The other ideas don’t fit because blocking COX-2 reversibly wouldn’t produce the strong, lasting antiplatelet effect seen with aspirin, platelet aggregation is primarily driven by COX-1–derived thromboxane in platelets, and antagonizing the ADP receptor or promoting plasminogen activation are mechanisms of other therapies (P2Y12 inhibitors and fibrinolytics, respectively).

Aspirin’s antiplatelet effect comes from irreversibly inhibiting COX-1 in platelets, which lowers thromboxane A2 production. Thromboxane A2 is a powerful promoter of platelet aggregation and vasoconstriction, so when COX-1 is blocked, platelets become less prone to clump together. The inhibition is irreversible because platelets lack a nucleus and cannot make new COX-1; as a result, the effect lasts for the platelet’s entire lifespan (about 7–10 days). Endothelial cells can synthesize new COX-1 and restore prostacyclin production over time, which helps balance bleeding risk.

The other ideas don’t fit because blocking COX-2 reversibly wouldn’t produce the strong, lasting antiplatelet effect seen with aspirin, platelet aggregation is primarily driven by COX-1–derived thromboxane in platelets, and antagonizing the ADP receptor or promoting plasminogen activation are mechanisms of other therapies (P2Y12 inhibitors and fibrinolytics, respectively).

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