Syntocinon: Uses, Dosage & Side Effects
Synthetic oxytocin for induction and augmentation of labor, and for the prevention and treatment of postpartum hemorrhage
Syntocinon is a brand name for synthetic oxytocin, a nonapeptide hormone chemically identical to the natural oxytocin produced by the posterior lobe of the pituitary gland. Oxytocin is one of the oldest and most widely used medicines in modern obstetrics. It binds to oxytocin receptors in the myometrium (the muscular wall of the uterus) and triggers rhythmic uterine contractions similar to those of natural labor. Syntocinon is used to induce labor when delivery is medically necessary, to augment labor when contractions are inadequate, and to prevent or treat postpartum hemorrhage caused by uterine atony. It is given only in hospitals and maternity units, typically as a carefully controlled intravenous infusion, with continuous monitoring of the fetal heart rate and uterine activity. Syntocinon is a prescription-only medicine (Rx) included on the World Health Organization's Model List of Essential Medicines.
Quick Facts: Syntocinon
Key Takeaways
- Syntocinon is synthetic oxytocin, chemically identical to the natural hormone that triggers uterine contractions during labor and milk ejection during breastfeeding.
- Its principal uses are induction of labor when delivery is medically indicated, augmentation of slow or inadequate labor, prevention of postpartum hemorrhage during the third stage of labor, and treatment of established bleeding from uterine atony.
- Syntocinon is always administered in a hospital setting, usually as a dilute intravenous infusion through a calibrated pump, with continuous electronic fetal and uterine monitoring to detect hyperstimulation and fetal distress.
- The main risks are uterine hyperstimulation (contractions that are too frequent, too long or too strong), fetal distress, water intoxication with severe hyponatremia (at high doses in large volumes of electrolyte-free fluid) and, very rarely, uterine rupture or cardiovascular collapse.
- Oxytocin is on the World Health Organization's Model List of Essential Medicines and is considered a cornerstone intervention for safe childbirth worldwide; correct dosing, careful monitoring and clear clinical indications are essential to its safety.
What Is Syntocinon and What Is It Used For?
Syntocinon contains oxytocin as its active ingredient. Oxytocin is a nine-amino-acid peptide hormone (a nonapeptide) naturally synthesized in the hypothalamus and released from the posterior lobe of the pituitary gland. In the body it plays a central role in two physiological processes: the uterine contractions that drive labor and delivery, and the milk-ejection reflex that allows milk to flow during breastfeeding. It also has a broader role in social bonding, pair formation and stress regulation, which is why oxytocin is sometimes called the “love hormone” in popular writing. Syntocinon is the pharmaceutical version: it is produced synthetically to be chemically identical to the natural hormone, so that it acts on the same receptors and produces the same physiological effects when administered clinically.
The clinical use of oxytocin dates back to the 1950s, when the chemist Vincent du Vigneaud first determined its sequence and achieved its chemical synthesis – work for which he received the Nobel Prize in Chemistry in 1955. Since then, synthetic oxytocin has become one of the most widely used medicines in obstetric care globally. It is included on the World Health Organization (WHO) Model List of Essential Medicines and is available in virtually every delivery unit in the world. Syntocinon is one of several commercial brand names; in the United States, the same active ingredient is most commonly sold under the brand name Pitocin, and generic oxytocin is widely available.
Syntocinon is approved and used for the following indications across the European Union, the United Kingdom, the United States and most other countries:
Induction of Labor
When a continued pregnancy poses greater risk to the mother or baby than delivery, labor may be induced with Syntocinon. Common medical indications include pregnancy that continues beyond 41–42 weeks (post-term pregnancy), prelabor rupture of membranes (“waters breaking” without contractions starting), pre-eclampsia or gestational hypertension, maternal diabetes, intrauterine growth restriction, chorioamnionitis (infection of the amniotic fluid), intrauterine fetal death, and certain maternal medical conditions that are worsened by pregnancy. Syntocinon is given as a carefully controlled intravenous infusion, starting at a low rate and increasing gradually until adequate uterine activity is established. It is often preceded by cervical ripening with a prostaglandin or mechanical methods when the cervix is not yet favorable for labor.
Augmentation of Labor
If labor has started spontaneously but contractions are too weak, too short or too infrequent to produce progressive cervical dilation, Syntocinon can be used to augment (strengthen) the contractions. This is commonly referred to as “inadequate uterine activity,” “failure to progress,” or “prolonged labor.” Augmentation with oxytocin is often used together with artificial rupture of the membranes (amniotomy). As with induction, the goal is to establish effective contractions – typically three to four strong contractions every ten minutes – while avoiding hyperstimulation. The decision to augment is made carefully, because many labors progress more slowly than the textbook curve but still result in normal vaginal delivery without intervention.
Prevention of Postpartum Hemorrhage
After the baby is delivered, the uterus must contract firmly to compress the blood vessels at the site where the placenta was attached. Failure of the uterus to contract well (uterine atony) is the leading cause of postpartum hemorrhage worldwide and accounts for a large proportion of maternal deaths in low- and middle-income countries. Active management of the third stage of labor, which includes giving a prophylactic dose of oxytocin (usually 5 or 10 IU) as an intramuscular injection or slow intravenous injection immediately after delivery, has been shown in multiple large randomized trials and Cochrane systematic reviews to significantly reduce the risk of postpartum hemorrhage and the need for blood transfusion. The WHO recommends oxytocin as the first-line uterotonic for this purpose.
Treatment of Postpartum Hemorrhage
If postpartum hemorrhage occurs despite prevention, Syntocinon is also used as a first-line treatment. A loading dose is given by slow intravenous injection, followed by a maintenance infusion to keep the uterus firmly contracted until bleeding is controlled. If oxytocin alone is not sufficient, additional uterotonics such as ergometrine, misoprostol or carbetocin may be added, and surgical or interventional radiology procedures may be required in severe cases. In all cases, rapid recognition and early treatment are essential.
Incomplete, Inevitable or Missed Miscarriage
Syntocinon may also be used to assist uterine emptying after an incomplete, inevitable or missed miscarriage, typically in combination with other treatments. Lower doses are used than for labor induction at term, because the uterus and its oxytocin receptors are less developed in early pregnancy and therefore respond differently.
Cesarean Section
Syntocinon is also used during and after cesarean delivery to promote uterine contraction once the baby has been delivered, helping to reduce blood loss. A standard dose of 5 IU is given by slow intravenous injection after delivery of the baby (not before), often followed by a maintenance infusion.
Oxytocin binds to specific G-protein coupled oxytocin receptors (OXTR) in the smooth muscle cells of the uterine myometrium. Activation triggers a cascade involving phospholipase C, inositol trisphosphate (IP3), and release of calcium from intracellular stores. The increased intracellular calcium activates myosin light chain kinase, producing smooth muscle contraction. Importantly, the density of oxytocin receptors in the uterus increases more than a hundred-fold during pregnancy and peaks at term, which is why the pregnant uterus at term is exquisitely sensitive to oxytocin, while the non-pregnant or early-pregnant uterus is relatively resistant.
What Should You Know Before Receiving Syntocinon?
Contraindications
There are clinical situations in which Syntocinon must not be used because the risks to mother or baby outweigh any potential benefit. Understanding these contraindications is essential for patient safety.
- Hypersensitivity: Do not use Syntocinon if you have a known allergy to oxytocin or to any of the other ingredients (excipients) in the formulation.
- Hypertonic uterine contractions: Syntocinon must not be given when uterine contractions are already hypertonic, tetanic or excessively frequent, as this may worsen the condition and threaten the fetus.
- Mechanical obstruction to delivery: Do not use Syntocinon when mechanical factors prevent safe vaginal delivery – for example, marked cephalopelvic disproportion, transverse fetal lie, or a vaginal tumor obstructing the birth canal.
- Fetal distress without imminent delivery: Syntocinon should not be used when the fetus shows signs of distress and delivery is not expected imminently, as stronger contractions would worsen fetal oxygen deprivation.
- Predisposition to uterine rupture: Syntocinon is generally contraindicated in any condition that carries a high risk of uterine rupture – for example, previous classical (vertical) cesarean section, previous uterine rupture, grand multiparity, or major uterine malformations. The use of oxytocin for vaginal birth after low transverse cesarean section (VBAC) is possible but requires careful individualized assessment.
- Placenta previa and vasa previa: These conditions are contraindications to attempting vaginal delivery and therefore to labor induction or augmentation with Syntocinon.
- Cord presentation or prolapse: Labor induction with Syntocinon is contraindicated if the umbilical cord is presenting or has prolapsed, because of the acute risk of fetal compromise.
- Severe toxemia / eclampsia: In severe pre-eclampsia or eclampsia, Syntocinon is used only when delivery is clinically necessary and the maternal condition is stabilized. Fluid balance must be monitored carefully because of the risk of water intoxication.
- Oxytocin resistance: In rare cases where a prolonged adequate trial of oxytocin fails to induce labor, continued administration is not helpful and may be harmful.
Warnings and Precautions
The most important acute complication of Syntocinon is uterine hyperstimulation – contractions that are too frequent (more than five in 10 minutes), too long (lasting more than 60–90 seconds), or too strong, with inadequate relaxation between contractions. Hyperstimulation reduces placental blood flow and can cause fetal heart rate abnormalities, hypoxia, and in rare cases uterine rupture. Continuous electronic fetal monitoring and uterine tocography are essential throughout Syntocinon infusion. If hyperstimulation occurs, the infusion must be reduced or stopped immediately and further measures (maternal repositioning, oxygen, tocolysis) taken as clinically indicated.
Talk to your medical team and make sure they are aware of your full medical history before Syntocinon is started, particularly if any of the following apply to you:
- Previous uterine surgery: Including cesarean section, myomectomy (removal of fibroids), repair of uterine perforation, or resection of a uterine septum. Your team will weigh the risks and benefits carefully.
- Grand multiparity: Women who have given birth five or more times have an increased risk of uterine rupture and require particularly cautious dosing.
- Heart problems: Rapid intravenous injection of oxytocin can cause transient hypotension, reflex tachycardia and arrhythmias. Patients with significant cardiovascular disease require careful evaluation.
- Pre-existing arrhythmias: Inform your team if you have a history of arrhythmia, QT-interval prolongation, or are taking drugs that affect heart rhythm.
- Kidney disease: Because oxytocin has mild antidiuretic properties at higher doses, patients with reduced kidney function may be at increased risk of water retention and hyponatremia.
- Porphyria: Oxytocin is considered potentially porphyrinogenic and should be used with caution in patients with acute porphyrias.
- Age over 35 or significant maternal comorbidities: Older maternal age and significant comorbidities are associated with higher baseline risks in labor and require individualized care.
Oxytocin has structural similarities to the antidiuretic hormone vasopressin and exerts a mild antidiuretic effect at higher doses. When Syntocinon is given in high doses and/or in large volumes of electrolyte-free fluid (such as 5% glucose in water) for prolonged periods, it can cause water retention, dilutional hyponatremia, seizures, coma and even death. To minimize this risk, Syntocinon should be diluted in an electrolyte-containing solution (for example, sodium chloride 0.9% or a balanced crystalloid), the total fluid volume and infusion rate should be controlled, total dose should be kept within recommended limits, and fluid balance should be monitored, especially during prolonged or high-dose infusions. Serum electrolytes may need to be checked in complex or prolonged labors.
Monitoring During Syntocinon Infusion
Syntocinon must be administered with continuous and careful monitoring. Standard observations include:
- Continuous electronic fetal heart rate monitoring (cardiotocography, CTG) to detect fetal distress early.
- Continuous or near-continuous recording of uterine contractions (external tocography or internal pressure monitoring), with attention to frequency, duration, intensity and baseline tone.
- Regular assessment of maternal pulse, blood pressure, respiratory rate and oxygen saturation.
- Monitoring of fluid balance (intake, output and any signs of fluid overload) with careful documentation.
- Regular assessment of progress in labor, including cervical dilation, fetal station and position.
Pregnancy and Breastfeeding
Syntocinon is only used during late pregnancy and in the immediate postpartum period. There is no indication for routine use of Syntocinon in early or mid-pregnancy. When used as recommended during labor and delivery, Syntocinon is considered safe and is an essential tool for the management of complicated labors and for reducing maternal mortality from postpartum hemorrhage.
Oxytocin passes into breast milk in very small amounts and is rapidly broken down in the infant's digestive tract. It is not considered a contraindication to breastfeeding. In fact, the natural release of oxytocin from the mother's pituitary gland during breastfeeding is what triggers milk let-down, and skin-to-skin contact with the baby stimulates this endogenous oxytocin release.
Children and Adolescents
Syntocinon is not indicated in non-pregnant children or adolescents. Its use is restricted to obstetric indications in pregnant women, some of whom may be adolescents. In pregnant adolescents, doses are the same as in adult women.
Driving and Operating Machinery
Syntocinon is administered in hospital during labor and delivery or in the immediate postpartum period; patients in this situation are not driving or operating machinery. After discharge, Syntocinon has been fully metabolized and has no expected residual effects on driving or machine operation.
How Does Syntocinon Interact with Other Drugs?
Syntocinon is a peptide hormone and is not metabolized by the hepatic cytochrome P450 enzymes, so interactions based on enzyme induction or inhibition (which are common with many other drugs) do not apply. Instead, the interactions that matter clinically are pharmacodynamic: other drugs that either potentiate or counteract oxytocin's effects on the uterus and cardiovascular system.
Major Interactions
| Interacting Drug | Effect | Clinical Significance |
|---|---|---|
| Prostaglandins (dinoprostone, misoprostol) | Synergistic uterotonic effect; may sensitize the uterus to oxytocin for several hours after administration | Do not start Syntocinon within 6 hours of vaginal or cervical prostaglandin administration; careful monitoring for hyperstimulation is essential |
| Volatile inhalational anesthetics (sevoflurane, desflurane, isoflurane) | Potentiate the hypotensive effect of oxytocin and may cause arrhythmias; may also relax the uterus, reducing oxytocin effectiveness | Use lower doses of oxytocin and monitor blood pressure and cardiac rhythm carefully during general anesthesia |
| Sympathomimetic vasoconstrictors (ephedrine, phenylephrine, adrenaline) | When combined with oxytocin – especially after caudal or spinal anesthesia with a sympathomimetic vasopressor – severe, sometimes fatal hypertension and intracranial hemorrhage have been reported | Avoid concurrent use; if both are required, monitor blood pressure intensively |
| QT-prolonging drugs (antiarrhythmics, some antidepressants, antipsychotics, macrolide antibiotics) | Theoretical increased risk of ventricular arrhythmias; oxytocin alone may prolong QT slightly at high doses | Use with caution in patients already taking QT-prolonging drugs; ECG monitoring may be appropriate |
Other Relevant Interactions
| Interacting Drug | Effect | Clinical Significance |
|---|---|---|
| Caudal or spinal anesthesia | May potentiate the hypotensive effect of oxytocin | Monitor blood pressure closely; administer oxytocin by slow infusion rather than rapid bolus |
| Caffeine | May theoretically enhance the pressor response; clinical significance is minimal at normal dietary doses | No specific restriction; high caffeine intake should be avoided in labor by usual obstetric practice |
| Ergot alkaloids (ergometrine/methylergometrine) | Combined with oxytocin produces stronger and more sustained uterine contraction (used therapeutically as the fixed combination Syntometrine in some regions for postpartum hemorrhage) | Deliberate combination is used clinically; risk of hypertension means ergometrine is contraindicated in hypertension and pre-eclampsia |
| Carbetocin (long-acting oxytocin analogue) | Cumulative uterotonic effect; not intended for simultaneous use | Choose one uterotonic; do not give both for the same indication |
| Large-volume electrolyte-free infusions (5% dextrose) | Increase the risk of dilutional hyponatremia and water intoxication due to the antidiuretic effect of oxytocin | Dilute Syntocinon in an electrolyte-containing solution; monitor fluid balance and electrolytes |
Because Syntocinon is given in a controlled hospital setting, your obstetric and anesthetic teams will carefully consider all of your medications, including any over-the-counter drugs, herbal supplements (such as blue cohosh or raspberry leaf), and recreational substances, when planning your care. Always provide a complete list of what you take.
What Is the Correct Dosage of Syntocinon?
Syntocinon dosing is always individualized, based on the indication, the response of the uterus and fetus, and the mother's overall clinical status. Dosing in labor is expressed in international units (IU) or milli-international units per minute (mIU/min); 1 IU of oxytocin corresponds to approximately 1.66 µg (micrograms), so an 8.3 µg/ml ampoule contains 5 IU/ml. Most national guidelines and manufacturer information use IU/mIU for clarity and safety. Medicines reconciliation and precise infusion-pump programming are critical.
Induction and Augmentation of Labor
Dilute IV Infusion for Labor Induction / Augmentation
Standard dilution: 10 IU of oxytocin added to 1000 ml of sodium chloride 0.9% or another electrolyte-containing infusion fluid, giving a concentration of 10 mIU/ml.
Starting dose: 1–4 milliunits per minute (mIU/min), corresponding to 6–24 ml/hour at the above concentration.
Titration: Increase in increments of 1–2 mIU/min at intervals of at least 30 minutes until adequate contractions are established (typically 3–4 contractions of 40–60 seconds every 10 minutes, with relaxation between contractions).
Usual maximum: 20 mIU/min. In selected cases, up to 32 mIU/min may be used in strict hospital settings, with close fetal and uterine monitoring.
Discontinuation: Reduce or stop the infusion if contractions become too frequent (>5 in 10 minutes), too long (>60–90 seconds) or if fetal heart rate abnormalities occur. The short half-life of oxytocin means uterine activity usually returns toward baseline within several minutes of stopping.
Prevention of Postpartum Hemorrhage
Prophylactic Oxytocin After Vaginal Delivery
Dose: 5 IU by slow intravenous injection or 10 IU by intramuscular injection, given after delivery of the anterior shoulder of the baby or immediately after birth.
Timing: Part of active management of the third stage of labor, along with controlled cord traction and uterine massage as appropriate.
Alternatives: In regions without a reliable cold chain for oxytocin, other uterotonics (misoprostol, carbetocin, oxytocin – ergometrine fixed combination) may be preferred. WHO recommends oxytocin as first-line where it is available and quality-assured.
Treatment of Postpartum Hemorrhage
Syntocinon for Established PPH due to Uterine Atony
Loading dose: 5 IU by slow intravenous injection.
Maintenance infusion: 20–40 IU added to 500–1000 ml of an electrolyte-containing infusion fluid, titrated to maintain firm uterine contraction.
Additional measures: Uterine massage, bladder emptying, intravenous fluid resuscitation, identification and treatment of other causes of PPH (tissue, trauma, thrombin), and escalation to other uterotonics and surgical interventions as needed. Protocols such as the “four T's” (tone, tissue, trauma, thrombin) guide rapid evaluation.
Cesarean Section
Syntocinon at Cesarean Delivery
Dose: 5 IU by slow intravenous injection given after delivery of the baby. Some protocols use a lower initial dose (for example 1–3 IU) in women with significant cardiovascular disease to minimize hypotension, followed by a maintenance infusion.
Maintenance infusion: 10 IU in 500 ml of a balanced electrolyte solution at a controlled rate, particularly for women at high risk of uterine atony (prolonged labor, chorioamnionitis, multiple gestation, polyhydramnios, grand multiparity).
Management of Incomplete or Missed Miscarriage
When Syntocinon is used to assist uterine emptying in the setting of miscarriage, the dose is typically 10 IU added to 500 ml of an electrolyte-containing solution, infused at 20–40 drops per minute (or the equivalent mIU/min). Higher doses may be needed because the uterus is less sensitive to oxytocin in early pregnancy. Syntocinon is often used together with misoprostol or a surgical procedure (dilation and curettage, or manual vacuum aspiration) depending on clinical circumstances and local guidelines.
Dose Adjustments and Special Populations
- Elderly: Oxytocin in non-obstetric contexts is not indicated in elderly patients. In advanced-age pregnancies, the same obstetric dosing principles apply, with closer cardiovascular monitoring.
- Renal impairment: Oxytocin is largely eliminated by non-renal mechanisms, but its antidiuretic effect becomes more clinically important in patients with reduced kidney function. Careful fluid management is essential.
- Hepatic impairment: No specific dose adjustment is required for hepatic impairment.
- VBAC (vaginal birth after cesarean): If Syntocinon is used at all, lower maximum doses and careful titration are recommended; many guidelines advise using the minimum effective dose.
Missed Dose
Because Syntocinon is administered only in hospital by healthcare professionals, the concept of a patient-missed dose does not apply. If an infusion is interrupted (for example, because of hyperstimulation or equipment issues), the clinical team will restart at a lower rate and titrate up again according to uterine and fetal response.
Overdose
Overdose of Syntocinon produces predictable problems: uterine hyperstimulation with strong, prolonged or tetanic contractions, fetal distress, and in severe cases uterine rupture, placental abruption, amniotic fluid embolism (rarely), maternal hypotension and – with prolonged high-dose infusions in large fluid volumes – water intoxication with severe hyponatremia and seizures. Treatment consists of immediate discontinuation of Syntocinon, supportive care (oxygen, repositioning, fluid restriction in cases of hyponatremia, hypertonic saline in severe hyponatremia with seizures), and prompt delivery of the baby if fetal distress is confirmed. Tocolysis (for example with terbutaline) may be used to relax the uterus in selected cases.
Syntocinon must never be self-administered. It is given only by qualified doctors or midwives in an equipped obstetric unit with the ability to monitor the fetus and mother continuously, to deliver the baby urgently if needed, and to manage postpartum hemorrhage. Dosing involves calibrated infusion pumps and strict medication-safety procedures. “Do-it-yourself” induction of labor with Syntocinon is extremely dangerous and never appropriate.
What Are the Side Effects of Syntocinon?
Like all medicines, Syntocinon can cause side effects, although not every patient will experience them. The frequency categories below follow the Council for International Organizations of Medical Sciences (CIOMS) classification. Some effects are related to the expected pharmacological action of oxytocin on the uterus (for example, hyperstimulation), while others reflect effects on the cardiovascular system, water balance, or occasional allergic responses.
Very Common
May affect more than 1 in 10 people
- Nausea
- Vomiting
- Uterine contractions (expected pharmacological effect)
Common
May affect up to 1 in 10 people
- Headache
- Tachycardia (fast heart rate)
- Bradycardia (slow heart rate)
- Cardiac arrhythmia
- Uterine hyperstimulation (contractions too frequent, too long, or too strong) – may require dose reduction
- Fetal heart rate abnormalities (usually secondary to hyperstimulation)
Uncommon
May affect up to 1 in 100 people
- Skin rash
- Flushing
- Hypotension, especially with rapid IV injection
Rare
May affect up to 1 in 1,000 people
- Anaphylactic or anaphylactoid reaction, including bronchospasm, hypotension, angioedema and shock
- Water intoxication with severe dilutional hyponatremia, associated with headache, drowsiness, confusion, convulsions and – in severe cases – coma and death
- Postpartum hemorrhage due to paradoxical uterine atony after prolonged infusion
- Disseminated intravascular coagulation (DIC), particularly in the context of severe pre-eclampsia, placental abruption or amniotic fluid embolism
Very Rare
May affect up to 1 in 10,000 people
- Cardiac arrhythmias of severe clinical significance, including ventricular tachycardia
- Ischemic ECG changes and, in isolated cases, myocardial ischemia
- Uterine rupture, particularly in women with risk factors such as previous uterine surgery, high parity or hyperstimulation
Not Known
Frequency cannot be estimated from available data
- Pulmonary edema (especially in the context of water intoxication or fluid overload)
- QT-interval prolongation
- Neonatal jaundice, neonatal hyponatremia and low Apgar scores at 5 minutes (observational associations, causality complex)
- Neonatal retinal hemorrhage
Fetal and Neonatal Effects
Syntocinon does not cross the placenta in large amounts and has no direct effect on the fetal or neonatal brain. However, the uterine contractions it produces reduce placental blood flow briefly with each contraction, and excessive contractions can reduce fetal oxygen delivery. Most adverse fetal effects – including fetal distress, low Apgar scores, and the need for neonatal resuscitation or admission to neonatal intensive care – are linked to uterine hyperstimulation rather than to any direct drug effect on the fetus. Careful dose titration and continuous fetal monitoring are therefore critical.
It is important to report any suspected side effects to your healthcare provider. Reporting helps regulatory authorities continuously monitor the benefit-risk balance of medicines. You can also report side effects directly to your national pharmacovigilance agency (for example, the FDA MedWatch program in the United States, the MHRA Yellow Card scheme in the United Kingdom, the EMA EudraVigilance system in the European Union, or Health Canada's MedEffect program).
How Should Syntocinon Be Stored?
Proper storage of Syntocinon is essential to maintain its potency. Oxytocin is a peptide that is sensitive to heat and light; quality of the medicine can degrade significantly if stored incorrectly, leading to reduced clinical effect. As a hospital-administered medication, storage is managed by pharmacy and nursing staff, but the basic principles are:
- Unopened ampoules: Store in the refrigerator at 2–8°C (36–46°F) in the original carton to protect from light. Do not freeze. Formulations that allow storage at room temperature for a limited period (up to 25–30°C) are available in some countries; check the specific product information.
- After opening and dilution: The diluted infusion should ideally be used immediately. If not used immediately, storage times and conditions depend on the specific formulation and local guidelines – typically no more than 24 hours at 2–8°C and 6 hours at room temperature, protected from light.
- Cold chain: In many low-resource settings, reliable refrigeration of oxytocin is a significant challenge. Heat-stable carbetocin (an oxytocin analogue) has been developed and is recommended by WHO as an alternative uterotonic where the oxytocin cold chain cannot be maintained.
- Expiry date: Do not use Syntocinon after the expiry date printed on the carton and ampoule. The expiry date refers to the last day of the stated month.
- Keep out of reach of children.
- Disposal: Any unused product or waste material should be disposed of in accordance with local regulations.
Healthcare facilities should monitor fridge temperatures, rotate stock to use older ampoules first, and audit the quality of oxytocin regularly, because substandard or falsified oxytocin is a recognized public health concern, particularly in regions with weaker pharmaceutical supply chains.
What Does Syntocinon Contain?
Understanding what Syntocinon contains is useful for identifying potential allergens and understanding how different formulations compare.
- Active substance: Oxytocin (synthetic). Each millilitre contains either 5 IU (8.3 µg) or 10 IU (16.7 µg) of oxytocin depending on the specific product; typical ampoules are 1 ml.
- Excipients: Commonly include chlorobutanol hemihydrate (a preservative, 5 mg/ml in some traditional formulations), acetic acid and/or sodium acetate (for pH adjustment), and water for injection. Preservative-free formulations are available in some regions for epidural, intrauterine, or infant use; they typically contain just oxytocin, a buffer and water for injection.
- Appearance: Clear, colorless solution without visible particles.
- Presentation: Glass ampoules, typically 1 ml, supplied in packs of 5 or 10 ampoules. Concentrations vary by region and indication.
- Marketing authorization holder: Varies by country – Novartis/Sandoz, Alfasigma or other manufacturers hold the license in different jurisdictions.
Brand Names and Generic Equivalents
Synthetic oxytocin is sold under several brand names worldwide. The most widely recognized include:
- Syntocinon – the original brand name, used in most of Europe, Australia, Canada and many other countries.
- Pitocin – the most common brand name in the United States.
- Oxytocin injection – generic versions are widely available in most countries.
- Syntometrine (oxytocin 5 IU + ergometrine 0.5 mg) – a fixed combination used in some countries for active management of the third stage of labor.
- Pabal / Duratobal / Duratocin (carbetocin) – a long-acting oxytocin analogue used particularly in cesarean delivery and in settings where the cold chain for oxytocin cannot be maintained.
While the active substance and IU-based dosing are equivalent across these products for their shared indications, always follow the specific prescribing information for the product used in your hospital.
Chemical Structure
Oxytocin is a nonapeptide with the amino-acid sequence Cys–Tyr–Ile–Gln–Asn–Cys–Pro–Leu–Gly-NH₂, stabilized by a disulfide bond between the two cysteine residues. Its molecular formula is C₄₃H₆₆N₁₂O₁₂S₂ and its molecular mass is approximately 1007 Da. Oxytocin differs from the antidiuretic hormone vasopressin by only two amino acids, which explains why it retains some antidiuretic activity at high concentrations.
Frequently Asked Questions About Syntocinon
Yes, the oxytocin molecule in Syntocinon is chemically identical to the oxytocin made by your pituitary gland. It is a nine-amino-acid peptide with exactly the same sequence and three-dimensional structure as the natural hormone. However, there are some important practical differences between synthetic oxytocin given by infusion and natural oxytocin released by your own body during labor. Natural oxytocin is released in a pulsatile pattern, crosses the blood-brain barrier to a limited extent, and is part of a broader neuroendocrine cascade involving beta-endorphins and other hormones. Syntocinon infusions deliver a steady plasma concentration and do not replicate this pulsatile pattern. These differences may explain why labor augmented with Syntocinon sometimes feels more intense than spontaneous labor, and why adequate pain relief options should be discussed with your team.
Contractions during Syntocinon-augmented labor are often described as more intense and possibly closer together than spontaneous contractions, although individual experiences vary widely. The likely reasons include the steady (rather than pulsatile) delivery of the hormone, the fact that natural labor builds up gradually while Syntocinon can establish strong contractions relatively quickly, and the underlying obstetric situation that required induction or augmentation. Pain management options – including breathing techniques, water immersion, transcutaneous electrical nerve stimulation (TENS), nitrous oxide, opioid analgesia, and epidural anesthesia – are as available during Syntocinon labor as during spontaneous labor. Discuss your preferences with your team before labor starts.
The uterus usually starts to respond within a few minutes of the Syntocinon infusion being started, although reaching adequate contractions typically takes 30–60 minutes because the dose is deliberately titrated upward in small steps to avoid hyperstimulation. For postpartum indications, a slow IV injection of oxytocin begins to contract the uterus within about 1 minute, and an intramuscular injection begins working within 3–7 minutes. The plasma half-life of oxytocin is only a few minutes, so when the infusion is stopped, the uterine effect also diminishes rapidly.
Current evidence does not show a clear, consistent effect of Syntocinon used during labor on mother-infant bonding or long-term breastfeeding outcomes. Some observational studies have suggested associations between intrapartum synthetic oxytocin and small differences in early breastfeeding initiation or behavioral outcomes, but the evidence is inconsistent and may reflect the underlying reasons for induction or augmentation rather than a direct drug effect. Skin-to-skin contact immediately after birth, early breastfeeding, and rooming-in promote your own oxytocin release and are the most effective ways to support bonding and breastfeeding initiation. If you have concerns, talk to your midwife or obstetrician.
Uterine rupture is a very rare but serious complication of labor. The risk is increased by a previous cesarean section, previous uterine surgery, high parity, uterine malformations and by hyperstimulation from any uterotonic including Syntocinon. The overall risk of uterine rupture in women without previous uterine surgery given standard-dose Syntocinon is extremely low. In women attempting a vaginal birth after cesarean (VBAC), the background risk of rupture is around 0.5%, and use of oxytocin can slightly increase this; careful dose titration, avoidance of hyperstimulation, and continuous monitoring are essential. Classical (vertical) cesarean scars, previous uterine rupture and certain other surgical histories are generally considered contraindications to Syntocinon-augmented labor.
Oxytocin and vasopressin (antidiuretic hormone) are both nonapeptide hormones produced in the hypothalamus and released from the posterior pituitary. They differ in only two amino acids. Oxytocin's main actions are on the uterus and mammary gland, triggering uterine contraction and milk ejection; vasopressin's main actions are on the kidneys (water reabsorption) and blood vessels (vasoconstriction). Because of their similarity, oxytocin retains a mild antidiuretic effect at higher doses – which is the reason water intoxication is a risk when high doses are given in large volumes of electrolyte-free fluid. This is why clinicians dilute Syntocinon in an electrolyte-containing solution and limit the total fluid volume during prolonged infusions.
All information is based on international medical guidelines, regulatory approvals, and peer-reviewed clinical literature: the European Medicines Agency (EMA) Summary of Product Characteristics, the U.S. Food and Drug Administration (FDA) prescribing information for oxytocin/Pitocin, the World Health Organization (WHO) recommendations on induction of labour and on prevention and treatment of postpartum haemorrhage, the UK National Institute for Health and Care Excellence (NICE) guideline NG207 on inducing labour, the American College of Obstetricians and Gynecologists (ACOG) Practice Bulletins on labor induction and postpartum hemorrhage, the International Federation of Gynecology and Obstetrics (FIGO) recommendations, and Cochrane systematic reviews on uterotonics for labor induction and PPH prevention.
References
- European Medicines Agency (EMA). Oxytocin (Syntocinon) – Summary of Product Characteristics (SmPC). National product information, harmonized EU text, last revised 2025.
- U.S. Food and Drug Administration (FDA). Pitocin (oxytocin injection, USP) – Prescribing Information. Last updated 2024.
- World Health Organization. WHO Recommendations on Induction of Labour, at or Beyond Term. Geneva: World Health Organization; 2022. Available at: who.int/publications/i/item/9789240052796
- World Health Organization. WHO Recommendations for the Prevention and Treatment of Postpartum Haemorrhage. Geneva: World Health Organization; 2022.
- National Institute for Health and Care Excellence (NICE). Inducing Labour – NICE Guideline NG207. London: NICE; 2021, updated 2023.
- American College of Obstetricians and Gynecologists (ACOG). Practice Bulletin No. 107: Induction of Labor. Obstetrics & Gynecology. 2009;114(2 Pt 1):386-397 (reaffirmed and updated periodically).
- American College of Obstetricians and Gynecologists (ACOG). Practice Bulletin No. 183: Postpartum Hemorrhage. Obstetrics & Gynecology. 2017;130(4):e168-e186 (with subsequent updates).
- Alfirevic Z, Kelly AJ, Dowswell T. Intravenous oxytocin alone for cervical ripening and induction of labour. Cochrane Database of Systematic Reviews. 2009;(4):CD003246. doi:10.1002/14651858.CD003246.pub2
- Westhoff G, Cotter AM, Tolosa JE. Prophylactic oxytocin for the third stage of labour to prevent postpartum haemorrhage. Cochrane Database of Systematic Reviews. 2013;(10):CD001808. doi:10.1002/14651858.CD001808.pub2
- du Vigneaud V, Ressler C, Swan JM, Roberts CW, Katsoyannis PG. The synthesis of oxytocin. Journal of the American Chemical Society. 1953;75(19):4879-4880.
- Dyer RA, van Dyk D, Dresner A. The use of uterotonic drugs during caesarean section. International Journal of Obstetric Anesthesia. 2010;19(3):313-319. doi:10.1016/j.ijoa.2010.04.011
- World Health Organization. WHO Model List of Essential Medicines – 23rd List, 2023. Geneva: World Health Organization; 2023.
- Bell AF, Erickson EN, Carter CS. Beyond labor: the role of natural and synthetic oxytocin in the transition to motherhood. Journal of Midwifery & Women's Health. 2014;59(1):35-42. doi:10.1111/jmwh.12101
- International Federation of Gynecology and Obstetrics (FIGO). FIGO Recommendations on the Management of Postpartum Hemorrhage 2022. International Journal of Gynecology & Obstetrics. 2022;157(Suppl 1):3-50.
Editorial Team
Medical Content
iMedic Medical Editorial Team – Specialists in Obstetrics, Maternal-Fetal Medicine and Clinical Pharmacology
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iMedic Medical Review Board – Independent panel following WHO, EMA, FDA, FIGO and NICE guidelines
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Level 1A – Based on systematic reviews, meta-analyses, Cochrane reviews and randomized controlled trials
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– Updated according to current EMA SmPC, FDA prescribing information, WHO and NICE guidance
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