oxytocin
Brand: Pitocin, Syntocinon
ISMP High Alert Prototype Drug
Drug Class: oxytocic agent
Drug Family: uterotonic
Subclass: synthetic posterior pituitary hormone
Organ Systems: endocrinereproductive
Mechanism of Action
Binds oxytocin receptors in the myometrium, activating phospholipase C and increasing intracellular calcium, causing uterine contractions. Increases frequency and strength of contractions. Also stimulates milk ejection reflex via action on mammary myoepithelial cells.
oxytocin receptor (OXTR) in myometriummyoepithelial cells in mammary gland
Indications
- induction of labor at term
- augmentation of labor (insufficient contractions)
- prevention and treatment of postpartum hemorrhage
- management of incomplete/inevitable abortion
Contraindications
- fetal malpresentation (some)
- placenta previa
- prior classic uterine incision
- contraindications to vaginal delivery
Adverse Effects
Common
- uterine hyperstimulation (contractions too frequent/too long)
- nausea
- vomiting
- fetal heart rate abnormalities
Serious
- uterine rupture
- hyponatremia (with excess IV fluid — antidiuretic effect at high doses)
- fetal distress/asphyxia
- hypotension (rapid IV bolus)
- amniotic fluid embolism (rare)
Pharmacokinetics (ADME)
| Absorption | IV infusion; nasal spray for milk letdown |
| Distribution | distributed to extracellular fluid |
| Metabolism | plasma oxytocinase (oxytocinase enzyme) and hepatic metabolism |
| Excretion | renal |
| Half-life | 1–6 minutes |
| Onset | immediate (IV) |
| Peak | minutes |
| Duration | 1 hour (after stopping infusion) |
| Protein Binding | 30% |
| Vd | 0.3 L/kg |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| vasoconstrictors | additive vasopressor effects; severe hypertension when given with vasoconstrictors | major |
| prostaglandins | additive uterotonic effect; risk of excessive uterine stimulation | major |
Nursing Considerations
- Administer via IV infusion pump ONLY; titrate rate in small increments every 20–40 minutes based on contraction frequency; never administer as a rapid IV bolus in labor (hypotension risk).
- Monitor uterine contractions (should not exceed 5 in 10 minutes), fetal heart rate, and maternal vital signs continuously.
- If uterine hyperstimulation occurs: stop infusion, position patient in left lateral decubitus, provide oxygen, notify provider.
- For postpartum hemorrhage: 10–40 units in 1L IV fluid at a rate sufficient to control uterine atony; monitor for hyponatremia with large volumes.
Clinical Pearls
- Oxytocin is the single most common cause of preventable harm in obstetrics — overdose causes uterine tachysystole, uterine rupture, and fetal hypoxia; proper infusion pump management and continuous electronic fetal monitoring are mandatory.
- At doses used for postpartum hemorrhage, oxytocin has significant antidiuretic (ADH-like) properties; large volumes of hypotonic IV fluids with high-dose oxytocin can cause life-threatening dilutional hyponatremia.
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Not required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.