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# Uterotonics (oxytocin and analogues)

Oxytocin and its long-acting analogue carbetocin make the uterus contract. They are the first-line medicines to prevent and treat bleeding after birth.

Updated 2026-11-01

## What they are

Peptides that act on the oxytocin receptor of the myometrium. Oxytocin induces or strengthens labour and, with carbetocin, prevents and treats postpartum haemorrhage due to uterine atony, a major cause of maternal death.

## Mechanism of action

They bind the oxytocin receptor, a Gq-coupled receptor on uterine smooth muscle. Phospholipase C makes IP3, calcium rises inside the cell and the myometrium contracts more often and more strongly. After birth, a firm uterus squeezes the vessels of the placental bed and stops the bleeding. Because they resemble vasopressin, they also have an antidiuretic effect that can retain water.

Target: Oxytocin receptor (OXTR)

## Key points

- Oxytocin is the WHO first choice to prevent postpartum haemorrhage; heat-stable carbetocin is the alternative.
- Main risks: uterine hyperstimulation (fetal distress, uterine rupture) and water intoxication with low sodium.
- Oxytocin must be refrigerated; heat-stable carbetocin does not need a cold chain.
- In the WHO trial, carbetocin was given as a single injection right after the birth of the baby.
- Prostaglandins add to their effect on the uterus.

## Drugs in this class

- [**Oxytocin** Synthetic copy of the posterior pituitary hormone that makes the uterus contract: used to induce labour and to prevent… Oxytocin receptor (OXTR)](https://durgical.com/en/pharmacology/oxytocin/)

## Others in the class

- Demoxytocin
- Carbetocin

## Test yourself

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

## Which receptor and second messenger mediate the uterine contraction caused by oxytocin?

The oxytocin receptor, coupled to Gq: phospholipase C makes IP3, intracellular calcium rises and the myometrium contracts.

## Why can oxytocin cause water intoxication?

It resembles vasopressin and has an antidiuretic effect; with long infusions and a lot of fluid, water is retained and sodium falls.

## What practical advantage does heat-stable carbetocin have over oxytocin?

It does not need refrigeration, so it keeps working where the cold chain fails.

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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: [Global health agencies issue new recommendations to help end deaths from postpartum haemorrhage](https://www.who.int/news/item/05-10-2025-global-health-agencies-issue-new-recommendations-to-help-end-deaths-from-postpartum-haemorrhage) (World Health Organization, 2025); [DailyMed - OXYTOCIN injection, solution](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=4c4c4b69-8bf7-472c-aafe-29805ba5c965) (DailyMed (U.S. National Library of Medicine), 2026); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=H01BB) (WHO Collaborating Centre for Drug Statistics Methodology, 2026); [WHO study shows drug could save thousands of women’s lives](https://www.who.int/news/item/27-06-2018-who-study-shows-drug-could-save-thousands-of-women%E2%80%99s-lives) (World Health Organization, 2018).

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