What is the mechanism of action of tranexamic acid (TXA)?

• A. Inhibits the binding of plasminogen to fibrin, stabilizing clot formation
• B. Activates plasmin to dissolve clots
• C. Increases platelet aggregation
• D. Causes vasoconstriction

Answer: (A)

Tranexamic acid acts as an antifibrinolytic by blocking the interaction between plasminogen/plasmin and fibrin. It is a lysine analog that competitively binds to the lysine-binding sites on plasminogen (and plasmin), preventing plasmin from attaching to fibrin. Without plasmin binding, fibrin breakdown is slowed, so formed clots remain more stable and bleeding is reduced. It does not activate plasmin, increase platelet aggregation, or cause vasoconstriction. This mechanism helps stabilize clots in surgical bleeding, trauma, and heavy menstrual bleeding scenarios.