Syntocinon

Action

Unknown. Thought to directly stimulate smooth muscle contractions in uterus and cervix.

Availability

Injection: 10 units/ml ampule or vial

Indications and dosages

➣ To induce or stimulate labor

Adults: Initially, 1-ml ampule (10 units) in compatible I.V. solution infused at 1 to 2 milliunits/minute (0.001 to 0.002 units/minute). Increase rate in increments of 1 to 2 milliunits/minute q 15 to 30 minutes until acceptable contraction pattern is established.

➣ To control postpartum bleeding

Adults: 10 to 40 units in compatible I.V. solution infused at rate adequate to control bleeding; or 10 units I.M. after placenta delivery

➣ Incomplete abortion

Adults: 10 units in compatible I.V. solution infused at 10 to 20 milliunits/minute (0.01 to 0.02 units/minute)

Off-label uses

• Antepartal fetal heart rate testing

• Breast enlargement

Contraindications

• Hypersensitivity to drug

• Cephalopelvic disproportion

• Fetal distress when delivery is not imminent

• Prolonged use in uterine inertia or severe toxemia

• Hypertonic or hyperactive uterine pattern

• Unfavorable fetal position or presentation that's undeliverable without conversion

• Labor induction or augmentation when vaginal delivery is contraindi-cated (as in invasive cervical cancer, active genital herpes, or total placenta previa)

Precautions

Use cautiously in:

• previous cervical or uterine surgery, history of uterine sepsis

• breastfeeding patients.

Administration

• Reconstitute by adding 1 ml (10 units) to 1,000 ml of normal saline solution, lactated Ringer's solution, or dextrose 5% in water.

See Don't give by I.V. bolus injection.

• Infuse I.V. using controlled-infusion device.

• Be aware that drug isn't routinely given I.M.

• Know that drug should be given only to inpatients at critical care facilities when prescriber is immediately available.

Adverse reactions

CNS: seizures, coma, neonatal brain damage, subarachnoid hemorrhage

CV: premature ventricular contractions, arrhythmias, neonatal bradycardia

GI: nausea, vomiting

GU: postpartal hemorrhage; pelvic hematoma; uterine hypertonicity, spasm, or tetanic contraction; abruptio placentae; uterine rupture (with excessive doses)

Hematologic: afibrinogenemia

Hepatic: neonatal jaundice

Other: hypersensitivity reactions including anaphylaxis, low 5-minute Apgar score (neonate)

Interactions

Drug-drug. Sympathomimetics: postpartal hypertension

Thiopental anesthetics: delayed anesthesia induction

Vasoconstrictors: severe hypertension (when given within 3 to 4 hours of oxytocin)

Drug-herbs. Ephedra (ma huang): increased hypertension

Patient monitoring

See Continuously monitor contractions, fetal and maternal heart rate, and maternal blood pressure and ECG. Discontinue infusion if uterine hyper-activity occurs.

See Monitor patient extremely closely during first and second stages of labor because of risk of cervical laceration, uterine rupture, and maternal and fetal death.

• When giving drug to control postpartal bleeding, monitor and record vaginal bleeding.

• Assess fluid intake and output. Watch for signs and symptoms of water intoxication.

Patient teaching

• Inform patient about risks and benefits of oxytocin-induced labor.

See Teach patient to recognize and immediately report adverse drug effects.

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