oxytocin

Oxytocin used as medication is a synthetic form of the natural human hormone oxytocin produced by the hypothalamus region in the brain and secreted into the bloodstream by the pituitary gland. Oxytocin is used to induce or improve uterine contractions during delivery and to prevent uncontrolled bleeding (hemorrhage) after the delivery. Oxytocin may also be used to eliminate the uterine contents after a spontaneous or induced termination of pregnancy.

Oxytocin is naturally secreted by the body to produce uterine contractions during childbirth, and synthetic oxytocin works likewise. Oxytocin works on positive feedback. The release of oxytocin causes uterine contractions, which in turn, cause more oxytocin to be released, increasing the intensity and frequency of contractions, enabling a vaginal delivery.

Oxytocin binds to oxytocin receptors in the uterine muscle wall (myometrium) and stimulates contraction by increasing influx of calcium ions in the uterine muscle cells. Oxytocin receptor concentration normally increases during pregnancy, with levels peaking at term when labor starts. The response to oxytocin varies between individuals depending on the concentration of oxytocin receptors in the uterus.

Oxytocin also causes contraction of the myoepithelial cells in the breasts, which helps eject the milk out. The baby’s attempt to suck sends positive feedback, which in turn stimulates oxytocin release and milk output. Oxytocin also has antidiuretic and vasodilatory effects, increasing fluid balance and improving blood flow. In the brain, oxytocin acts as a neurotransmitter and plays an important role in human behaviors including romantic attachment, sexual arousal, trust, mother-child and other relationship bonding.

Oxytocin is approved for use in induction of labor in pregnant women at term or near term in certain circumstances:

• The mother has certain medical conditions including:
  • Preeclampsia, a serious high blood pressure condition that can develop during pregnancy
  • Diabetes
  • Rhesus (Rh) factor incompatibility with the baby
  • Premature rupture of the membranes
• The mother’s uterus is inactive at term and requires stimulation to start labor
• The mother has an inevitable or incomplete abortion in her second trimester
• Oxytocin is approved for use in the third stage of labor, after the baby’s birth (postpartum), to aid expulsion of the placenta and prevent postpartum hemorrhage.

• Oxytocin is not approved for use in elective induction of labor, when there are no medical indications for inducing labor
• Oxytocin administration for induction of labor and improving uterine contractions should only be administered intravenously under medical supervision
• Do not administer oxytocin in the following circumstances:
  • Patients with hypersensitivity to oxytocin
  • Fetal distress where delivery is not imminent
  • Adequate uterine activity fails to achieve satisfactory progress
  • Uterus is already hyperactive or has too much muscle tone (hypertonic)
  • Significant disproportion in the size and shape of the baby’s head and mother’s pelvis (cephalopelvic disproportion)
  • Unfavorable fetal position or presentation, such as a transverse lie, which is undeliverable without conversion to a head down position
  • Obstetrical emergencies which require a surgical intervention
  • Medical conditions in which vaginal delivery should not be performed, such as invasive cervical carcinoma and active genital herpes
  • Pregnancy and labor complications such as partial or total placenta previa, vasa previa, cord presentation or prolapse of the cord
  • Prematurity, fetal distress, or excessive amniotic fluid (polyhydramnios)
  • In women who have experienced pregnancies exceeding 20 weeks and labor five or more times (multiparity), have had previous major surgery of the cervix or uterus including caesarian section, or a history of uterine sepsis or traumatic delivery
• Excessive stimulation of the uterus can result in increased intensity and frequency of contractions, which can result in uterine rupture, cervical and vaginal tear, hemorrhage and fetal injury; monitor closely and discontinue oxytocin if the uterus is overstimulated
• Severe water intoxication in the mother with seizure, coma and death has been reported with slow oxytocin infusion over 24 hours; use with caution and restrict fluid intake, if required
• Oxytocin use has an increased risk of blood loss and impairment of blood clotting process (afibrinogenemia) in the mother

Common side effects of oxytocin include:

Mother

• Serious allergic reaction (anaphylactic reaction)
• Premature ventricular contractions
• Postpartum hemorrhage
• Pelvic hematoma
• Irregular heart rhythms (cardiac arrhythmia)
• Bleeding in the space between the brain and its membrane (subarachnoid hemorrhage)
• Fatal afibrinogenemia
• Hypertensive episodes
• Nausea
• Vomiting
• Rupture of the uterus

Fetal/neonate

Due to induced uterine contractions

• Slow heartbeat (bradycardia)
• Premature ventricular contractions and other arrhythmias
• Low tissue oxygen saturation in the fetus (fetal hypoxia)
• High carbon dioxide levels in the fetus (fetal hypercapnia)
• Permanent central nervous system (CNS) or brain damage
• Fetal death
• Neonatal seizures (rare)

Due to use of oxytocin in the mother

• Low Apgar scores at five minutes; Apgar score is how a baby’s condition is assessed immediately after birth
• Neonatal jaundice
• Neonatal retinal hemorrhage
• Perinatal liver tissue death (necrosis)

This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug.

Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.

Injectable Solution

• 10 units/mL

Postpartum Hemorrhage

• 10 unit intramuscularly (IM) after delivery of the placenta
• Add 10-40 units; not to exceed 40 units; to 1000 mL of non-hydrating intravenous (IV) solution and infuse at the necessary rate to control uterine atony

Labor Induction

• 0.5-1 mUnit/min IV, titrate 1-2 mUnit/min q15-60min until contraction pattern reached that is similar to normal labor (usually 6 mUnits/min); may decrease dose after the desired frequency of contraction reached and labor has progressed to 5-6 cm dilation

Incomplete or Inevitable Abortion

• 10-20 mUnit/min; not to exceed 30 units/12 hours

Monitor

• Intrauterine pressure, fetal heart rate

• Oxytocin overdose may be a result of excess dosage or hypersensitivity of the uterus.
• Excessive stimulation of uterine contractions can result in strong and prolonged contractions resulting in tumultuous labor, uterine rupture, cervical and vagina tears and postpartum hemorrhage in the mother, and injure and asphyxiate the fetus, which may even lead to perinatal death.
• Large doses for prolonged periods can result in water intoxication with convulsions, because of the antidiuretic effect of oxytocin.
• Treatment includes immediate discontinuation of oxytocin and symptomatic and supportive therapies for both mother and newborn.

Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.

• Oxytocin has no known severe interactions with other drugs
• Serious Interactions of oxytocin include:
  • fexinidazole
  • lefamulin
  • mefloquine
  • misoprostol
• Oxytocin has moderate interactions with at least 29 different drugs.
• Oxytocin has no known minor interactions with other drugs

The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.

It is important to always tell your doctor, pharmacist, or health care provider of all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or health care provider if you have any questions about the medication.

• Oxytocin may be used for approved indications at term or near term of pregnancy.
• Oxytocin should not be used otherwise during pregnancy except when required to eliminate uterine contents after an inevitable or incomplete abortion in the second trimester of pregnancy.
• Oxytocin may be present in milk; breastfeeding should be delayed for at least 1 day after discontinuation of oxytocin.