What is the recommended aspirin dosage for myocardial infarction?

• A. 325 mg PO
• B. 324 mg PO
• C. 100 mg PO
• D. 500 mg PO

Answer: (B)

Aspirin is given in acute myocardial infarction to rapidly inhibit platelet aggregation by irreversibly blocking COX-1, which reduces thromboxane A2 formation and helps prevent further clot growth. To get a quick antiplatelet effect, a single loading dose around 300 mg is used, with the tablet form chewed to speed absorption. The commonly accepted amount in many protocols is 324 mg total, usually taken as four 81 mg chewables. Chewing and using a non-enteric coating ensure faster onset than a split or swallowed tablet, so this single-dose approach provides prompt protection during the critical early minutes of a suspected MI.