oxytocin

oxytocin /oxy·to·cin/ (-to´sin) a hypothalamic hormone stored in the posterior pituitary, which has uterine-contracting and milk-releasing actions; it may also be prepared synthetically or obtained from the posterior pituitary of domestic animals; used to induce active labor, increase the force of contractions in labor, contract uterine muscle after delivery of the placenta, control postpartum hemorrhage, and stimulate milk ejection.

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ox·y·to·cin (ks-tsn)

n.

A short polypeptide hormone that is released from the posterior lobe of the pituitary gland, stimulates the contraction of smooth muscle of the uterus during labor, and facilitates release of milk from the breast during nursing.

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Oxytocin

A hormone that stimulates the uterus to contract during child birth and the breasts to release milk.

Mentioned in: Antepartum Testing, Pituitary Dwarfism, Stillbirth

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oxytocin (kˈ·sē·tōˑ·sin),

n hormone that plays a role during pregnancy, delivery, and lactation and influences other relationships such as care taking and parental or pair bonding.

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oxytocin (ok´sētō´sin),

n a hormone of the posterior pituitary gland that is the principal uterus-contracting hormone. Used in obstetrics to induce uterine contractions.

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oxytocin

a hypothalamic hormone stored in and released from the posterior pituitary, or prepared synthetically. Produced also by the corpus luteum of sheep, and perhaps other animals. Involved in the release of PGF_2α which induces luteolysis. It acts as a powerful stimulant to the pregnant uterus, especially toward the end of gestation. The hormone also causes milk to be expressed from the alveoli into the lactiferous ducts during suckling.

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oxytocin

Pitocin

Pharmacologic class: Posterior pituitary hormone

Therapeutic class: Uterine-active agent

Pregnancy risk category NR

FDA Boxed Warning

• Drug isn't indicated for elective induction of labor (defined as initiation of labor in pregnant woman with no medical indications for induction). Available data aren't adequate to evaluate benefits versus risk.

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 contraindicated (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.
☞ 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.

Route	Onset	Peak	Duration
I.V.	Immediate	40 min	1 hr
I.M.	3-5 min	40 min	2-3 hr

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

☞ Continuously monitor contractions, fetal and maternal heart rate, and maternal blood pressure and ECG. Discontinue infusion if uterine hyperactivity occurs.
☞ 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.
☞ Teach patient to recognize and immediately report adverse drug effects.

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oxytocin

Endocrinology A nonapeptide hormone which stimulates contraction of uterine smooth muscles and promotes milk ejection in females. Cf ADH.