Pharmacology · Class
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)
Drugs in this class
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.
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 (World Health Organization, 2025); DailyMed - OXYTOCIN injection, solution (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); WHO study shows drug could save thousands of women’s lives (World Health Organization, 2018).
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Representative model, for educational purposes only.