Obstetrics & Gynaecology/Uterotonic

Uterotonics (PPH)

also: oxytocin · Syntocinon · ergometrine · carboprost · misoprostol · Syntometrine

Overview

Drugs that contract the uterus — active management of the third stage and treatment of atonic postpartum haemorrhage. The escalation order and the agent-specific contraindications are heavily tested.

Mechanism

Oxytocin binds myometrial oxytocin receptors → rhythmic contraction (first-line). Ergometrine (ergot alkaloid) causes sustained tetanic contraction via α-adrenergic/5-HT receptors. Carboprost (PGF₂α) and misoprostol (PGE₁ analogue) stimulate prostaglandin-mediated contraction.

Indications

Active management of 3rd stage of labour
Postpartum haemorrhage (uterine atony)
Misoprostol/oxytocin: also miscarriage management

The agents

Oxytocin (Syntocinon)1st-line

IV/IM

First choice for prevention + treatment of PPH.

Ergometrineergot alkaloid

IM/IV

AVOID in hypertension/pre-eclampsia (vasoconstriction). Often combined as Syntometrine.

Carboprost (Hemabate)PGF₂α

deep IM, repeatable

AVOID in asthma (bronchospasm).

MisoprostolPGE₁

oral/SL/PR

Heat-stable; useful where injectables unavailable.

Adverse effects

Oxytocin: hypotension + reflex tachycardia (rapid IV), hyponatraemiacommon

Ergometrine: nausea/vomiting + hypertensionclassic

Carboprost: bronchospasm, flushing, diarrhoeaclassic

Misoprostol: pyrexia, shivering, diarrhoeacommon

Cautions & contraindications

Ergometrine in hypertension / pre-eclampsia / eclampsiaall

Vasoconstriction → dangerous BP rise.

Carboprost in asthmaasthma

Prostaglandin → bronchospasm.

Interactions

Avoid stacking vasoconstrictors with ergometrine

Monitoring & kinetics

Uterine tone, blood loss, BP, pulse

Escalation in atonic PPH: uterine massage → oxytocin → ergometrine → carboprost → misoprostol → surgical (alongside tranexamic acid).

Source: RCOG — PPH (Green-top 52) · BNF — Myometrial stimulants