Pharmacology · Prostaglandin analogues (obstetric use)

Misoprostol !

Prostaglandin E1 analogue tablet that contracts the uterus and softens the cervix, and protects the stomach. Heat-stable; on the WHO essential list.

Updated 2026-11-01

Class: Prostaglandin analogues (obstetric use)
Receptor: Prostaglandin E receptor EP3 (and other EP receptors)
ATC code: G02AD06
WHO Model List of Essential Medicines

Prostaglandin E receptor EP3 (and other EP receptors)Misoprostol

Crystal structure of the human EP3 receptor with misoprostol free acid, the active form of misoprostol.

Target in 3D: Prostaglandin E receptor EP3 (and other EP receptors). PDB structure 6M9T (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Misoprostol is converted to misoprostol acid, which binds prostaglandin E (EP) receptors. In the uterus it causes contractions and softens and opens the cervix; in the stomach it reduces acid secretion and strengthens mucosal defence. These actions explain its uses in obstetrics and in the prevention of ulcers caused by NSAIDs.

Misoprostol is converted to the active misoprostol acid
It binds EP receptors of the myometrium and cervix
The uterus contracts and the cervix softens and opens
In the stomach: less acid and more mucosal protection

Pharmacokinetics

Absorption: Rapid by mouth (also given vaginally, buccally or sublingually); food lowers the peak
Metabolism: Quickly de-esterified to misoprostol acid, the active form
Elimination: Mostly in urine
Half-life: About 20–40 minutes (misoprostol acid)
Onset and duration: Peak levels about 12 minutes after an oral dose

Indications

Prevention and treatment of postpartum haemorrhage where oxytocin is not available or cannot be used safely Postpartum haemorrhage →
Management of incomplete miscarriage Miscarriage (early pregnancy loss) →
Medical abortion, together with mifepristone (WHO essential list)
Induction of labour (low-dose vaginal tablet on the WHO list)
Prevention of NSAID-induced gastric ulcers in high-risk patients Peptic ulcer disease →

Adverse effects

Common

Diarrhoea and abdominal pain (common, usually early and short-lived)
Nausea, vomiting and flatulence
Fever and shivering
Headache

Contraindications

Pregnancy when used to prevent NSAID ulcers
Allergy to prostaglandins

Key interactions

Oxytocin and other oxytocic drugs: Misoprostol augments their effect; oxytocin is not started within 4 hours of misoprostol
Antacids containing magnesium: Worse diarrhoea

What is monitored

Contractions, fetal heart rate and cervical change when used for induction
Blood loss and uterine tone after birth
Temperature (fever and shivering are common) and hydration if diarrhoea
Confirmation that the uterus is empty after use for miscarriage

Administration and safety

Tablets are heat-stable and need no cold chain, which makes misoprostol useful in rural and low-resource settings.
Route varies with the indication (oral, buccal, sublingual, vaginal); the route and timing come from the protocol in use.
A previous caesarean or other uterine scar raises the risk of rupture; this is checked before use.
Do not give oxytocin within 4 hours of misoprostol.

Nursing care

Before use for induction: check for a uterine scar, fetal heart rate and contractions.
During induction: monitor contractions and the fetal heart rate; report hyperstimulation.
After birth or miscarriage: check uterine tone, bleeding, temperature and pain.
Teaching: shivering, fever and diarrhoea are expected; heavy bleeding, severe pain or persistent fever need prompt review.
In ulcer prevention: confirm the patient is not pregnant and explain that the medicine can cause abortion.

Pregnancy and breastfeeding

It causes uterine contractions: it can cause abortion, birth defects and uterine rupture, so it is not used in pregnancy for ulcer prevention.

Test yourself

Think of the answer, then tap the question to see it.

Why is misoprostol useful for postpartum haemorrhage in rural settings?

It is a heat-stable tablet that needs no cold chain or injection; WHO lists it when oxytocin is not available or cannot be used safely.

What is the active form of misoprostol?

Misoprostol acid, formed quickly by de-esterification.

Which uterine scar increases the risk of rupture with misoprostol?

A previous caesarean section or other uterine surgery.

Which two non-obstetric effects explain misoprostol's use with NSAIDs?

Less gastric acid secretion and stronger mucosal protection.

Add to my cards (4)

← Back to the class: Prostaglandin analogues (obstetric use)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - MISOPROSTOL tablet (DailyMed (U.S. National Library of Medicine), 2026); eEML - Electronic Essential Medicines List (World Health Organization, 2025); Global health agencies issue new recommendations to help end deaths from postpartum haemorrhage (World Health Organization, 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.