Tranexamic Acid in Obstetric Haemorrhage
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Direct answer
Tranexamic acid is a synthetic lysine analogue that blocks plasminogen from binding to fibrin, which prevents clot breakdown. In obstetric haemorrhage it is given as 1 g intravenously over at least 10 minutes, with a second 1 g dose after 30 minutes if bleeding continues or restarts. Its benefit in reducing death from bleeding depends on giving it within three hours of birth.
What you must remember
- Mechanism: Competitively blocks the lysine binding sites on plasminogen, so fibrin is not broken down by plasmin.
- Dose: 1 g intravenously, given slowly over at least 10 minutes, and a second 1 g dose after 30 minutes if bleeding continues or restarts.
- Timing: The benefit is seen when started within three hours of birth, and later use has not shown a proven benefit.
- Route: Intravenous is the standard route for postpartum haemorrhage.
- Contraindications: Active thromboembolic disease and known hypersensitivity; a past thrombosis is a relative caution.
- Adverse effects: Nausea and diarrhoea, and rarely seizures or thrombosis with rapid or high-dose administration.
- Access: Tranexamic acid is on the WHO Model List of Essential Medicines and is used in postpartum haemorrhage programmes.
How tranexamic acid works in the clot
Fibrinolysis is the normal breakdown of clot, and bleeding after birth is worsened when this process becomes excessive. Tranexamic acid interrupts it at an early step, before fibrin is cut into degradation products.
- Plasminogen binds fibrin: Plasminogen attaches to lysine residues on fibrin, where it can be converted to plasmin.
- Plasmin cuts fibrin: Plasmin splits fibrin into degradation products, which loosens the clot and reopens vessels at the placental bed.
- Tranexamic acid blocks binding: The drug occupies the lysine binding sites on plasminogen, so it cannot attach to fibrin.
- Clot stays intact: With plasmin formation reduced, the clot remains stable and bleeding from the placental bed slows.
Because the effect depends on early use, tranexamic acid is part of the initial bundle given with uterotonics. It is not a rescue drug for bleeding that has continued for hours.
Doses are timed from the moment of birth, so the time of delivery should be written clearly in the notes.
Where the exam tries to catch you
Expect questions on the timing window, the second dose and the contraindications.
- Trap: Giving tranexamic acid as a substitute for uterotonics. Correct: It is an adjunct to oxytocin and surgical measures, and it does not treat uterine atony by itself.
- Trap: Repeating doses routinely without a clinical reason. Correct: The second 1 g dose is given only when bleeding continues or restarts, as the protocol directs.
- Trap: Starting tranexamic acid more than three hours after birth and expecting benefit. Correct: The benefit depends on early administration, so late use is not expected to reduce death from bleeding.
- Trap: Prescribing it to a woman with a previous thromboembolism without review. Correct: Active thromboembolism is the contraindication, while past thrombosis is a relative caution, so the risk is weighed with the physician.
Frequently asked questions
What is the dose of tranexamic acid in postpartum haemorrhage?
The standard dose of tranexamic acid in postpartum haemorrhage is 1 g intravenously, given slowly over at least 10 minutes. A second 1 g dose is given after 30 minutes if bleeding continues or restarts. Both doses are intravenous and are given as early as possible after birth.
Within how many hours of birth should tranexamic acid be given?
Tranexamic acid should be given within three hours of birth. The WOMAN trial showed a reduction in death from bleeding when the drug was started early, and later administration did not show that benefit. Early treatment is therefore part of the postpartum haemorrhage bundle.
Why is tranexamic acid contraindicated in active thromboembolic disease?
Tranexamic acid stabilises clots by blocking fibrinolysis, so it is contraindicated in active thromboembolic disease, and past venous or arterial thrombosis calls for caution. Thrombotic events are the main safety concern. The dose is also reduced in renal impairment because the drug is cleared by the kidneys.
Does tranexamic acid treat postpartum haemorrhage on its own?
No, tranexamic acid does not replace uterotonic drugs, mechanical measures or surgery in postpartum haemorrhage. It reduces bleeding by stabilising the clot and works alongside oxytocin and the other interventions. The cause of the haemorrhage, usually atony, still needs to be treated directly.