Aspirin has which of the following actions?

• A. Antibiotic
• B. Anticoagulant
• C. Diuretic
• D. Antihistamine

Answer: (B)

Aspirin reduces clot formation by preventing platelet aggregation. It does this by irreversibly inhibiting the enzyme COX-1 in platelets, which lowers production of thromboxane A2, a key promoter of platelet activation and aggregation. Because platelets can’t synthesize new COX-1, this effect lasts for the platelets’ lifespan (about 7–10 days). Clinically, this antiplatelet action is considered an anticoagulant/antithrombotic effect, which is why aspirin is described in this category. It is not an antibiotic (does not kill bacteria), not a diuretic (no major diuretic effect), and not an antihistamine (no histamine receptor blockade).