Tranexamic acid is a synthetic lysine amino acid derivative, which diminishes the dissolution of
hemostatic fibrin by plasmin. In the presence of tranexamic acid, the lysine receptor binding sites of
plasmin for fibrin are occupied, preventing binding to fibrin monomers, thus preserving and stabilizing
fibrin’s matrix structure.
The antifibrinolytic effects of tranexamic acid are mediated by reversible interactions at multiple binding
sites within plasminogen. Native human plasminogen contains 4 to 5 lysine binding sites with low
affinity for tranexamic acid (K d = 750 µmol/L) and 1 with high affinity (Kd = 1.1 µmol/L). The high
affinity lysine site of plasminogen is involved in its binding to fibrin. Saturation of the high affinity
binding site with tranexamic acid displaces plasminogen from the surface of fibrin. Although plasmin
may be formed by conformational changes in plasminogen, binding to and dissolution of the fibrin matrix
is inhibited.