Tranexamic acid
Breakdown · detail · Lysine analogue Within 3 hours
A synthetic lysine analogue that saturates the lysine-binding kringle sites of plasminogen, so plasminogen and t-PA can no longer dock onto fibrin. Plasmin is therefore never generated at the clot surface and the clot is protected from lysis. It is an antifibrinolytic, not a procoagulant.
Traced from the start
- Tissue factor and the extrinsic triggerVitamin K cycle and gamma-carboxylation
- Contact activation system (factor XII, prekallikrein, high-molecular-weight kininogen)
- Subendothelial collagen and von Willebrand factor
- Tissue factor-factor VIIa complex (extrinsic tenase)Factor IXaFactor VIIIa and its von Willebrand factor carrierActivated platelet phospholipid surface
- Factor XaFactor VaProthrombin (factor II)
- Thrombin (factor IIa)
- Plasminogen and tissue plasminogen activator
- Tranexamic acid
Detail
- Mechanism
- Competitive blockade of the lysine-binding sites of plasminogen, preventing its binding to fibrin
- Trauma evidence
- CRASH-2 showed reduced death from bleeding in trauma when given within 3 hours of injury, without excess vascular occlusive events
- Obstetric evidence
- The WOMAN trial showed reduced death from bleeding in postpartum haemorrhage when given within 3 hours of delivery
- Other uses
- Menorrhagia, dental extraction in haemophilia and von Willebrand disease, epistaxis, and prophylaxis in hereditary angioedema
- Cautions
- Avoid in upper urinary tract bleeding, where clot retention can obstruct the ureter; seizures occur at high doses in cardiac surgery
When it goes wrong
Tranexamic acid given more than 3 hours after injury or after delivery
No mortality benefit and possible harm — the entire benefit lies within the first 3 hours, which is why it is given at the roadside or on arrival rather than after imaging
Practise this structure
1 question in the bank tagged Fibrinolysis.