Uterotonic Drugs in Postpartum Haemorrhage
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Direct answer
Uterotonic drugs are agents that contract the uterus and form the first line of treatment for postpartum haemorrhage caused by uterine atony. Oxytocin is the first-line agent, given by intramuscular injection for the third stage and by intravenous infusion for treatment. Ergometrine, carboprost and misoprostol are second-line options, chosen according to contraindications, storage conditions and availability.
What you must remember
- First-line drug: Oxytocin, 10 IU intramuscularly in active management of the third stage, or an intravenous infusion for established atony.
- Ergometrine: 0.2 mg intramuscularly or slow intravenously (WHO and Indian practice; UK labels use up to 0.5 mg), contraindicated in hypertension, pre-eclampsia and cardiac disease, and needs refrigerated storage.
- Methylergometrine: 0.2 mg intramuscularly, a heat-sensitive alternative to ergometrine with the same contraindications.
- Carboprost: 250 mcg intramuscularly, repeatable at intervals, and contraindicated in asthma because it causes bronchospasm.
- Misoprostol: 800 mcg sublingually or rectally, heat-stable and useful where the cold chain is unreliable.
- Oxytocin toxicity: Hypotension and tachycardia with a rapid bolus, and water retention with prolonged high-volume infusion.
An escalation pathway for atony
Atony causes most postpartum haemorrhage, so drug choice follows a stepwise escalation. Each step begins only after the previous one has failed to produce firm uterine contraction.
- Confirm the cause: Massage the uterus, empty the bladder and check the placenta and genital tract for retained products or tears. Atony is a diagnosis of exclusion, so other causes must be looked for at the same time.
- Start oxytocin: Give 20 to 40 IU in 1 litre of crystalloid as an infusion at a rate that achieves uterine tone. A slow 5 IU bolus can be used when immediate effect is needed. Watch for hypotension and fluid overload.
- Add ergometrine or methylergometrine: Give 0.2 mg ergometrine or 0.2 mg methylergometrine intramuscularly only when blood pressure is normal and there is no hypertension, pre-eclampsia or cardiac disease.
- Add carboprost: Give 250 mcg intramuscularly, repeatable at intervals of 15 to 90 minutes up to a total of 8 doses. Do not use it in asthma.
- Give misoprostol: Use 800 mcg sublingually or rectally, particularly when other agents are unavailable or have failed. It can be combined with the other drugs.
- Move to mechanical or surgical measures: If uterine tone remains poor, proceed to balloon tamponade, compression sutures or arterial procedures, and hysterectomy as the final step.
Where the exam tries to catch you
Most questions on this topic hinge on a contraindication or a storage detail rather than on the dose.
- Trap: Choosing ergometrine for a woman with pre-eclampsia because it is the classic uterotonic. Correct: Ergometrine raises blood pressure and is contraindicated in hypertension and pre-eclampsia, so oxytocin or misoprostol is the safer choice.
- Trap: Giving carboprost to an asthmatic woman with atony. Correct: Carboprost causes bronchospasm and is contraindicated in asthma, so misoprostol or continued oxytocin is used instead.
- Trap: Giving oxytocin as a rapid IV bolus to a hypotensive patient. Correct: Rapid bolus causes hypotension, so oxytocin is given slowly, diluted, as an infusion.
- Trap: Assuming misoprostol needs a cold chain like ergometrine. Correct: Misoprostol is heat-stable, which is why it is valuable in community and low-resource settings.
Frequently asked questions
Which uterotonic is first line for postpartum haemorrhage?
Oxytocin is the first-line uterotonic for postpartum haemorrhage and is also the standard drug for active management of the third stage. It acts quickly on the myometrium and is given before the second-line agents. Ergometrine or misoprostol are added only when oxytocin fails.
Why is ergometrine avoided in hypertensive women?
Ergometrine causes sustained vasoconstriction and can raise blood pressure sharply, so ergometrine is avoided in hypertension, pre-eclampsia and cardiac disease. Methylergometrine carries the same restriction. Oxytocin or misoprostol are safer choices in these women.
What is the dose of misoprostol in postpartum haemorrhage?
Misoprostol for postpartum haemorrhage is commonly given as 800 mcg sublingually or rectally. Oral dosing is an alternative in some guidance. Its heat stability makes it valuable where refrigeration is unreliable, and shivering, fever and diarrhoea are its common side effects.
When is carboprost contraindicated in postpartum haemorrhage?
Carboprost is contraindicated in women with asthma because it causes bronchospasm. It needs caution in cardiac, hepatic or renal disease. It is refrigerated and is used when oxytocin and ergometrine-type drugs have not controlled the bleeding.
Why can oxytocin cause water intoxication?
Oxytocin has antidiuretic activity at high doses, so prolonged or high-volume infusion can cause water retention and hyponatraemia. This is why the infusion volume is limited and monitored in women with postpartum haemorrhage.