PharmacologyTier 2Medical Sciences concept

Tranexamic acid mechanism of action (antifibrinolytic)

Core concept

Synthetic lysine analogue - competitively blocks the lysine-binding sites on plasminogen, preventing its binding to fibrin -> inhibits plasmin-mediated fibrin degradation (antifibrinolytic)
Does not promote new clot formation - it stabilises existing clot by preventing its breakdown

Key detail

Used in: major trauma/haemorrhage (CRASH-2 - reduces death from bleeding if given <3h from injury), postpartum haemorrhage (WOMAN trial), menorrhagia, surgical bleeding (cardiac, orthopaedic), hereditary angioedema (adjunct), dental extraction in bleeding disorders (mouthwash)
No benefit - and possible harm - if given >3 hours after major trauma - the effect is time-critical
Renally cleared - dose reduction needed in renal impairment

Clinical relevance

Theoretical thrombosis risk historically limited use in some settings, but large trials (CRASH-2, WOMAN) showed no increase in thrombotic events at trauma/PPH doses
Relative contraindication in active thromboembolic disease and in haematuria of upper urinary tract origin (risk of clot retention/obstruction)
Distinct from desmopressin (releases stored factor VIII/vWF) - often used together in bleeding disorders

Correlations

Major haemorrhage protocol / trauma resuscitation
Postpartum haemorrhage management
Fibrinolysis and the coagulation cascade
Desmopressin mechanism (contrast)

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