Side by side

1. 1.Binds oxytocin receptors on uterine smooth muscle, causing coordinated contractions that increase in strength and frequency with dose.
2. 2.Acts on myoepithelial cells around breast ducts to trigger milk ejection during feeding.
3. 3.In the brain, oxytocin acts on reward and social-salience circuits — the basis for 'bonding' claims, which are far better established in animals than in people.
4. 4.It also has mild antidiuretic activity, which is why high doses with large fluid volumes can dilute sodium in the blood.

• Induction and augmentation of labour (approved)
• Prevention and treatment of postpartum haemorrhage (approved)
• Support of milk ejection (approved, intranasal in some countries)
• Autism and social behaviour (many small trials, mixed results)
• Anxiety, trust and pain perception in laboratory studies

• Reliable, dose-dependent uterine contractions
• Reduced bleeding after birth when used as part of active management of the third stage
• Small, inconsistent effects on social behaviour in autism trials, with the largest studies showing no clear benefit
• Intranasal studies in healthy volunteers show modest shifts in trust and attention to social cues

• Uterine hyperstimulation, which can distress the fetus
• Fetal heart-rate changes
• Water intoxication and low blood sodium at high doses with large fluid volumes
• Nausea and vomiting
• Headache
• Rare anaphylaxis
• Severe postpartum haemorrhage if bleeding is not managed correctly

Research context only — oxytocin is a hospital medicine given under continuous fetal and maternal monitoring, titrated in milli-units per minute. Intranasal doses of 24–40 IU were used in social-cognition research. It must never be self-administered for labour.

Research context only