DurgicalDurgical
EN
Open the app

Pharmacology · Uterotonics (oxytocin and analogues)

Oxytocin !

Synthetic copy of the posterior pituitary hormone that makes the uterus contract: used to induce labour and to prevent and treat bleeding after birth.

Updated 2026-11-01

Cryo-EM structure of the human oxytocin receptor with oxytocin bound and its Gq protein. Oxytocin is a peptide chain in this model, so there is no small-molecule ligand code.

Target in 3D: Oxytocin receptor (OXTR). PDB structure 7RYC (RCSB PDB, public domain). View the structure at RCSB PDB

Mechanism of action

Oxytocin binds the oxytocin receptor on uterine smooth muscle. The receptor activates Gq and phospholipase C, IP3 releases calcium and the myometrium contracts more often and more strongly. Before birth this induces or strengthens labour; after birth the contracted uterus closes the vessels of the placental bed. Its resemblance to vasopressin gives it an antidiuretic effect.

  1. Oxytocin binds the oxytocin receptor (Gq) of the myometrium
  2. Phospholipase C and IP3 raise intracellular calcium
  3. Contractions become more frequent and stronger
  4. After birth the firm uterus compresses the placental bed vessels

Pharmacokinetics

Absorption
Given IV (infusion) or IM; it is a peptide and is not given by mouth

Indications

Adverse effects

Common

  • Nausea and vomiting
  • Premature ventricular contractions and other arrhythmias
  • Low 5-minute Apgar scores in the newborn
  • Neonatal jaundice and retinal haemorrhage after induced labour

Contraindications

  • Significant cephalopelvic disproportion or an unfavourable fetal position (such as transverse lie)
  • Fetal distress when delivery is not imminent
  • Hypertonic uterine contractions
  • When vaginal birth is contraindicated: cord prolapse, total placenta previa, vasa previa
  • Obstetric emergencies where surgery is the better option
  • Prolonged use in uterine inertia or severe pre-eclampsia
  • Hypersensitivity to oxytocin

Key interactions

Vasoconstrictors given with caudal block anaesthesia
Severe hypertension has been reported
Misoprostol and other prostaglandins
They add to the uterine effect; giving them close together raises the risk of hyperstimulation
Carbetocin or methylergometrine
Cumulative uterotonic effect
Inhalational anaesthetics (cyclopropane, halothane)
Unexpected hypotension and rhythm changes; halothane also weakens the uterine response

What is monitored

  • Continuous fetal heart rate during induction or augmentation
  • Frequency, duration and strength of contractions and resting uterine tone
  • Maternal blood pressure and heart rate
  • Fluid intake and output, and serum sodium during long infusions
  • Uterine tone and blood loss after birth

Administration and safety

  • High-alert medicine: for induction or augmentation, only by IV infusion through an infusion pump, with an independent double check of the bag and pump settings.
  • Piggyback it into a running main line so it can be stopped at once without stopping the IV access.
  • Standard premixed bags and one concentration per unit reduce mix-ups.
  • Store in the refrigerator unless the label says otherwise; heat degrades it.
  • Look-alike risk: label clearly, because uterotonics have been given by mistake to newborns.

Nursing care

  • Before starting: check fetal position, cervix, a reactive fetal heart tracing and that vaginal birth is possible.
  • During infusion: watch contractions and the fetal heart rate continuously; trained staff stay at the bedside and a physician is immediately available.
  • Stop the infusion at once if contractions are too frequent or too long, or if the fetal heart rate is abnormal; turn the patient on her side, give oxygen and call the physician.
  • Watch for water intoxication: headache, drowsiness, confusion, low urine output and low sodium; record intake and output.
  • After birth: check uterine tone, fundal height and blood loss regularly.
  • Magnesium sulfate is often running at the same time in pre-eclampsia; check its own safety signs too.

Pregnancy and breastfeeding

Used at term and during labour, under monitoring; it is not meant for elective induction without a medical reason.

Test yourself

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

What is the first-line uterotonic to prevent postpartum haemorrhage according to WHO?

Oxytocin, with heat-stable carbetocin as the alternative; misoprostol is a last resort when IV options and a cold chain are unavailable.

What does the nurse do if the uterus is hyperstimulated during an oxytocin infusion?

Stops the infusion at once, turns the patient on her side, gives oxygen, watches the fetal heart rate and calls the physician.

Which electrolyte disorder appears with long oxytocin infusions, and why?

Low sodium from water intoxication: oxytocin has an antidiuretic effect similar to vasopressin.

Which are two contraindications to oxytocin for induction of labour?

Examples: cephalopelvic disproportion, transverse lie, cord prolapse, total placenta previa or vasa previa, and fetal distress when birth is not imminent.

Add to my cards (4)

← Back to the class: Uterotonics (oxytocin and analogues)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: DailyMed - OXYTOCIN injection, solution (DailyMed (U.S. National Library of Medicine), 2026); Global health agencies issue new recommendations to help end deaths from postpartum haemorrhage (World Health Organization, 2025); WHO recommendations: uterotonics for the prevention of postpartum haemorrhage (World Health Organization, 2018); eEML - Electronic Essential Medicines List (World Health Organization, 2025).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.