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[Pharmacology](https://durgical.com/en/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)

## Key points

- Mechanism: lysine analogues; block plasminogen binding to fibrin
- Tranexamic acid in postpartum haemorrhage (WHO) and trauma
- Avoid in active intravascular clotting (DIC without heparin) and upper urinary tract bleeding
- Excreted unchanged by the kidney: adjust in renal impairment
- Intravenous tranexamic acid given by the neuraxial route by mistake can cause seizures and arrhythmias

## Drugs in this class

- [**Tranexamic acid** A 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](https://durgical.com/en/pharmacology/tranexamic-acid/)
- [**Aminocaproic acid** An older lysine analogue antifibrinolytic used when excessive fibrinolysis causes bleeding, such as after heart or… Lysine-binding sites (kringle domains) of plasminogen](https://durgical.com/en/pharmacology/aminocaproic-acid/)

## 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.

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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](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=6f033f1e-8c78-4c87-b870-6493944315ff) (DailyMed (U.S. National Library of Medicine), 2026); [WHO recommendation on tranexamic acid for the treatment of postpartum haemorrhage](https://www.who.int/publications/i/item/9789241550154) (World Health Organization, 2017); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/) (World Health Organization, 2025).

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