Which medication is a platelet aggregation inhibitor?

• A. Clopidogrel (Plavix)
• B. Heparin
• C. Warfarin
• D. Enoxaparin

Answer: (A)

The main concept is how platelet aggregation inhibitors differ from anticoagulants. Clopidogrel works by blocking the P2Y12 ADP receptor on platelets, which prevents ADP-mediated activation of the glycoprotein IIb/IIIa complex and thus stops platelets from sticking together. This antiplatelet action directly reduces platelet aggregation, which is key in arterial thrombosis and in preventing events like heart attacks. The other medications are anticoagulants that work on the coagulation cascade rather than platelets: heparin enhances antithrombin III to inhibit thrombin and factor Xa; warfarin inhibits vitamin K-dependent clotting factor synthesis; enoxaparin mainly inhibits factor Xa with some anti-thrombin effects. So, clopidogrel is the platelet aggregation inhibitor.