The antithrombotic action of aspirin (acetylsalicylic acid) is due to inhibition of platelet function by acetylation of the platelet cyclooxygenase (COX) at the functionally important amino acid serine529.

What is the effect of aspirin on platelet function?

Aspirin acts on platelets by acetylating the cyclooxygenase enzyme at position serine 529, resulting in reduced formation of cyclic endoperoxides (prostaglandin G2 and prostaglandin H2) and thromboxane from arachidonic acid.

Does aspirin prevent platelet activation?

It seems that resistance to aspirin may be associated with an increase of arterial thrombotic events in spite of chronic intake. In ex vivo assays using aggregometry, with sodium arachidonate as agonist, aspirin inhibits platelet aggregation irreversibly in most people.