Pharmacology · Class
Antifibrinolytic haemostatics !
Lysine analogues that stop plasmin from dissolving a clot too early. They reduce bleeding in trauma, childbirth, surgery and heavy periods.
Updated 2026-11-01
What they are
Tranexamic acid and aminocaproic acid block the lysine-binding sites of plasminogen and plasmin, so these cannot bind fibrin. They do not make clots; they protect clots that form. Tranexamic acid is on the WHO essential list and is recommended by WHO for postpartum haemorrhage.
Mechanism of action
Plasminogen and plasmin attach to fibrin through lysine-binding sites in their kringle domains. These drugs mimic lysine and occupy the sites, inhibiting fibrinolysis.
Target: Plasminogen (lysine-binding sites)
Drugs in this class
- Tranexamic acidA lysine analogue that blocks clot breakdown. WHO recommends it for postpartum haemorrhage; it is also used in trauma…Lysine-binding sites (kringle domains) of plasminogen
- Aminocaproic acidAn older lysine analogue antifibrinolytic used when excessive fibrinolysis causes bleeding, such as after heart or…Lysine-binding sites (kringle domains) of plasminogen
Test yourself
Think of the answer, then tap the question to see it.
What amino acid do these drugs imitate?
Lysine.
Do antifibrinolytics form new clots?
No; they prevent the clots that form from being dissolved too early.
Why are they risky in upper urinary tract bleeding?
Clots that cannot be broken down can obstruct the ureters or kidney.
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 36 (McGraw Hill, 2023); DailyMed - TRANEXAMIC ACID injection, solution (DailyMed (U.S. National Library of Medicine), 2026); WHO recommendation on tranexamic acid for the treatment of postpartum haemorrhage (World Health Organization, 2017); eEML - Electronic Essential Medicines List (World Health Organization, 2025).
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Representative model, for educational purposes only.