Oxytocin
A synthetic form of the pituitary hormone, given by IV infusion or injection to induce labor and to prevent and treat bleeding after birth.
Drug card
- Class
- Oxytocic
- How it works
- Activating oxytocin receptors, so the uterus contracts
- Used for
- Inducing or strengthening labor (medical reasons only)
- Preventing and treating bleeding after birth
- Helping empty the uterus in incomplete miscarriage
- Known for
- Overstrong or too frequent contractions
- Water intoxication with low sodium (hyponatremia)
- Its name
- -tocin means an oxytocin analogue
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does oxytocin work?
Oxytocin binds oxytocin receptors in the myometrium and raises intracellular calcium, driving contraction through myosin light-chain kinase. The response depends on receptor density, which peaks in early labor at term. Its half-life is only minutes, so the effect of an IV infusion fades within about an hour of stopping; high doses have antidiuretic and pressor effects.
Uses
What is oxytocin used for?
- Inducing or strengthening labor (medical reasons only)
- Preventing and treating bleeding after birth
- Helping empty the uterus in incomplete miscarriage
Side effects
Side effects of oxytocin
- Overstrong or too frequent contractionsKnown forSerious
- Water intoxication with low sodium (hyponatremia)Known forSerious
- Uterine ruptureSerious
- Seizures from water intoxicationSerious
- Slow fetal heart rate and fetal distressSerious
- Nausea
- Vomiting
- Irregular heartbeat in the motherSerious
- Episodes of high blood pressureSerious
- Clotting failure (afibrinogenemia) with bleeding, rareSerious
- Severe allergic reaction (anaphylaxis)Serious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Not for elective induction: it is used for medical reasons, in hospital, by IV infusion with close supervision.
- Avoid with cephalopelvic disproportion, fetal distress, placenta previa or cord prolapse.
- Past cesarean section or other uterine surgery raises the risk of uterine rupture.
- Long infusions with large fluid volumes can cause water intoxication: monitor fluids and sodium.
Good to know: WHO recommends it as the uterotonic of choice for preventing postpartum hemorrhage at every birth.
Remember it
A way to remember it
Oxytocin is vasopressin's near twin.
The two hormones differ at only two amino acids, which is why large doses of oxytocin hold on to water and can cause hyponatremia and water intoxication.
Written for biofideX
Its name
-tocin means oxytocin analogue
Oxytocin and carbetocin share it. Atosiban, which blocks oxytocin receptors, ends in -siban instead.
- Every drug name stem
Its class
Oxytocin and its analogues
Oxytocin and its long-acting analogue carbetocin activate oxytocin receptors on uterine smooth muscle. Calcium inside the cells rises and the myometrium contracts more strongly and more often; receptor numbers climb through pregnancy, so the uterus at term responds most. Oxytocin also contracts the smooth muscle of the breast and, at high doses, acts like vasopressin to retain water.
Easily mixed up with prostaglandin analogues.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Oxytocin injection: label (DailyMed)
- Oxytocin (NCI Thesaurus)
- WHO updates guidance to help healthcare workers prevent postpartum haemorrhage (WHO)
- Global health agencies issue new recommendations to help end deaths from postpartum haemorrhage (WHO)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Reproductive and urinary health
Oxytocin is one of 9 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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