Brand name: Pitocin
Drug class: Oxytocics
VA class: GU600
CAS number: 50-56-6

Medically reviewed by Drugs.com on Aug 22, 2023. Written by ASHP.

Introduction

Oxytocic; indirectly stimulates contraction of uterine smooth muscle; elicits all the responses of endogenous oxytocin.

Uses for Oxytocin

Elective induction of labor (i.e., no medical indication for induction) merely for clinician or patient convenience is not a valid indication for oxytocin use.

IV infusion of dilute solutions is the method of choice for inducing labor at term and stimulating uterine contractions during the first and second stages of labor.

Labor Induction

Use for labor induction is indicated in term or near-term pregnancies associated with hypertension (e.g., preeclampsia, eclampsia, cardiovascular-renal disease), erythroblastosis fetalis, maternal or gestational diabetes mellitus, antepartum bleeding, premature placenta rupture (abruptio placentae) chorioamnionitis, or premature rupture of the membranes in which spontaneous labor does not ensue.

Routine induction of labor with oxytocin may be indicated in prolonged pregnancies (greater than 42 weeks’ gestation).

Eclampsia: if delivery is not imminent within 12 hours following an initial oxytocin infusion, consider cesarean section rather than continued oxytocin administration.

Induction of labor also may be indicated in cases of uterine fetal death (demise), fetal compromise (e.g., fetal growth retardation, isoimmunization), or static or decreasing maternal weight. However, may be relatively ineffective in cases of missed abortion, intrauterine fetal death in late pregnancy, benign hydatidiform mole, or fetuses with anencephaly or erythroblastosis fetalis with hydrops or other congenital abnormalities incompatible with life; some clinicians recommend intravaginal dinoprostone.

Induction of labor also may be indicated because of maternal medical conditions (e.g., diabetes mellitus, renal failure, COPD, chronic hypertension).

Carefully evaluate pelvic adequacy and other maternal and fetal conditions (including fetal lung maturity) whenever labor induction is considered.

If labor induction is indicated and cervical status is unfavorable, an agent for cervical ripening (e.g., dinoprostone) may be administered initially.

Do not use to induce labor when the benefit-to-risk ratio for the mother or child favors surgical intervention.

Labor induction and/or oxytocin may be contraindicated in certain fetal and/or maternal conditions. (See Contraindications)

Augmentation of Labor

May use during the first and second stages of labor to augment contractions if labor is prolonged or if dysfunctional uterine inertia (oxytocin usually not to exceed 6–8 hours) occurs.

Not recommended when labor is progressing normally during the first and second stages or when hypertonic patterns of labor occur, especially since drug response may be accentuated during the second stage of labor.

Do not use to augment labor when vaginal delivery is contraindicated (e.g., total placenta previa).

Postpartum Abbreviation of Third Stage of Labor

Has been used to shorten the third stage of labor immediately following delivery of the infant (when the absence of additional fetuses is established); oxytocin usually is recommended if an oxytocic is used for this purpose.

Oxytocics may inhibit rather than assist in placenta expulsion, and increase the risk of hemorrhage and infection.

Postpartum Control of Uterine Bleeding

Routinely used postpartum or following cesarean section to stimulate immediate uterine contractions and control uterine bleeding.

Postpartum hemorrhage and uterine atony: Ergonovine or methylergonovine usually preferred (due to more sustained contractions and higher uterine tonus) unless an immediate contractile response is desired.

IV oxytocin followed by an IM amine ergot alkaloid may be preferred.

Termination of Pregnancy

Has been used to shorten the induction-to-abortion time following prostaglandin or hypertonic abortifacients for induction of second trimester abortions; to induce abortion after failure to respond to the abortifacient; or to induce abortion after membrane rupture.

Has been used as an adjunct in incomplete abortion (when placenta fails to abort spontaneously within 1 hour after fetal abortion), but may hinder rather than assist in placental expulsion.

Usually, do not administer until the abortifacient oxytocic effect has subsided, and carefully monitor; concurrent use of oxytocin with abortifacients may produce intense uterine contractions that increase risk of uterine rupture or cervical laceration.

Evaluation of Fetal Respiratory Capability† [off-label]

Successfully used to evaluate the adequacy of fetal respiratory capabilities in high-risk pregnancies of >31 weeks gestation.

Transiently impedes uterine blood flow by inducing uterine contractions.

Positive response (late deceleration in fetal heart rate indicating chronic hypoxia) may occur if placental reserve is low.

Positive response may be fetal distress and may be indication for pregnancy termination, especially if a lecithin-sphingomyelin ratio >1.5 can be demonstrated.

Negative response (fetal heart rate unchanged) indicates adequate placental support is probably available.

Related/similar drugs

mifepristone, Pitocin, Methergine, Cervidil, methylergonovine, Hemabate, carboprost

Oxytocin Dosage and Administration

General

• Discontinue if prolonged uterine contractions (>90 seconds) or rising intrauterine pressure occur or if uterine motility interferes with fetal heart rate.

• Administer oxygen to the mother.

• Lateral position preferred for the mother; take other appropriate measures as necessary.

Administration

Administer by continuous or pulsatile IV infusion using a controlled-infusion device.

IM administration to augment or induce labor not recommended because effects it produces are unpredictable and difficult to control.

Administered IM to reduce postpartum uterine bleeding.

Do not give simultaneously by more than one route of administration.

IV Administration

Limit administration to trained personnel familiar with oxytocin’s effects.

Dilution

For IV infusion, must be diluted preferably in physiologic electrolyte solution (0.9% sodium chloride, lactated Ringer’s, or 5% dextrose injection, except under unusual circumstances).

For induction or augmentation of labor: Add 10 units (1 mL) to 1 L of appropriate infusion solution for 10 milliunits/mL.

For production of intense uterine contractions; to reduce postpartum bleeding; or as an adjunct to prostaglandin or hypertonic abortifacients: add 10 units (1 mL) to 500 mL of appropriate IV solution for 20 milliunits/mL.

For evaluation of fetal respiratory capability (oxytocin challenge test)^{† [off-label]}, add 5–10 units (0.5–1 mL) to 1 L of 5% dextrose injection for 5–10 milliunits/mL.

Rate of Administration

Determined by uterine response.

Continuous IV infusion, labor induction: Usually, initiate at 0.5–1 milliunit/minute for low-dose regimens or 6 milliunits/minute for high-dose regimens.

Pulsatile IV infusion, labor induction: Controlled-device pulse doses infused over 5–10-seconds at 5- to 8-minute intervals but no sooner than 30 seconds after contraction reaches baseline.

Continuous infusion, more intense uterine contractions: 10–100 millunits/minute, depending on use.

Dosage

Adults

Dosage is determined by uterine response.

Labor Induction

Continuous IV Infusion

Low-dose or high-dose regimens employed, depending on clinician preference.

Maximum dosage not established; titrate according to response and tolerance.

Monitor fetal heart rate and uterine contractions.

Low-dose regimens and less frequent dose increases associated with decreased uterine hyperstimulation.

High-dose regimens and more frequent dose increases associated with shorter labor, and less frequent cases of chorioamnionitis and cesarean delivery for dystocia but increased uterine hyperstimulation.

Low-dose: Usually, initiate at 0.5–1 milliunit/minute.

Generally, increase in low-dose regimen by 1- to 2-milliunits/minute at 30- to 60-minute intervals until a response is observed.

Low-dose: Alternatively, initiate at 1–2 milliunits/minute.

Generally, increase in alternative low-dose regimen by 2 millunits/minute at 15-minute intervals.

High-dose: Usually, initiate at about 6 milliunits/minute.

Generally, increase in high-dose regimen by about 6 milliunits at 15-minute intervals.

High-dose: Alternatively, initiate at 6 milliunits/minute.

Generally, increase in alternative high-dose regimen by 6, 3, or 1 millunits/minute at 20- to 40-minute intervals. If uterine hyperstimulation develops, do not exceed 3-milliunit/minute increases. If hyperstimulation recurs, do not exceed 1-millunit/minute increases.

May reduce infusion rate by similar amounts when the desired frequency of contractions is established (a uterine pattern comparable to spontaneous labor), without evidence of fetal distress, and labor has progressed to 5–6 cm dilation.

At term, employ higher rates of infusion with caution; rates >9–10 milliunits/minute rarely are required.

Before term, higher infusion rates may be necessary since uterine sensitivity to oxytocin is reduced secondary to decreased oxytocin receptors.

Pulsatile IV Infusion

Infused via controlled-infusion device as periodic rapid pulse doses.

Pulsatile dosing may better simulate spontaneous labor.

Pulsatile dosing may reduce the total dose needed.

Initiate at 1 milliunit/pulse (over 10 seconds) every 8 minutes for 3 doses per cycle, doubling the cycle dose as needed at 24-minute intervals (i.e., after each 3-dose cycle) until 32-milliunit pulse is achieved; thereafter, increase in 8-milliunit increments per cycle until adequate uterine activity is achieved.

Alternatively, a computer-controlled, feedback-loop dosing is used where doses range from 0.67–20 milliunits/pulse (over 5 seconds), repeated no more frequently than every 5 minutes and no sooner than 30 seconds aftera contraction reached baseline.

Initiate the alternative regimen at 0.67 millunits/pulse (over 5 seconds) every 5 minutes for 40 minutes; if inadequate labor, increase to 2 millunits/pulse every 5 minutes for 40 minutes. Subsequent increase by 1-milliunit/pulse no more frequently than after each 40-minute cycle. This regimen includes a computerized feedback loop measuring intrauterine waveform pressures to determine the timing of repeated doses.

Reduction of Postpartum Uterine Bleeding

Generally initiated after placental delivery and absence of additional fetuses is established.

IV

Infuse total of 10 units at 20–40 milliunits/minute; adjust rate to maintain uterine contraction and control uterine atony.

IM

10 units.

Pregnancy Termination

IV

Infuse at 10–100 milliunits/minute.

Maximum 30-unit cumulative dose within 12-hours because of water intoxication risk.

Evaluation of Fetal Respiratory Capability† [off-label]

Oxytocin Challenge Test to Evaluate Fetal Distress in High-Risk Pregnancy† [off-label]

IV

Initially, infuse at 0.5 milliunits/minute.

May gradually increase at 15- to 30-minute intervals to a maximum of 20 milliunits/minute.

Monitor fetal heart rate and uterine contractions immediately before and during oxytocin infusion.

Discontinue infusion and compare baseline and oxytocin-induced fetal heart rates when 3 moderate uterine contractions occur within a 10-minute interval.

Repeat in 1 week if no change in fetal heart rate occurs (negative response).

Termination of pregnancy may be indicated if late deceleration of fetal heart rate occurs.

Prescribing Limits

Adults

Labor Induction

No maximum dosage established.

Reduction of Postpartum Uterine Bleeding

IM

Total of 10 units.

IV

Usually, a total of 10 units.

Pregnancy Termination

IV

Maximum 30 units cumulative dose in 12-hours.

Oxytocin Challenge Test to Evaluate Fetal Distress† [off-label]

IV

Maximum of 20 milliunits/minute.

Cautions for Oxytocin

Contraindications

• Substantial cephalopelvic disproportion.

• Unfavorable fetal position or presentation (e.g., transverse lies) undeliverable without conversion before delivery.

• Obstetric emergencies where maternal or fetal risk-to benefit ratio favors surgery.

• Fetal distress when delivery is not imminent.

• Umbilical cord prolapse.

• Uterine activity fails to progress adequately.

• Hyperactive or hypertonic uterus.

• Vaginal delivery is contraindicated (e.g., invasive cervical carcinoma, active genital herpes infection, total placenta previa, vasa previa, cord presentation or prolapse).

• Uterine or cervical scarring from previous cesarean section or major cervical or uterine (e.g., transfundal) surgery.

• Unengaged fetal head.

• History of hypersensitivity to oxytocin or any ingredient in the formulation.

Warnings/Precautions

Warnings

Administer by qualified professional personnel in a hospital where intensive care and surgical facilities are immediately available.

High-risk Obstetic Situations

Not contraindicated but require special attention for oxytocic therapy in labor induction:

• ≥1 previous low-transverse cesarian deliveries

• breech presentation

• maternal heart disease

• multifetal pregnancy

• polyhydramnios

• presenting part above the pelvic inlet

• severe hypertension

• abnormal fetal heart rate patterns not necessitating emergent delivery

Sensitivity Reactions

Anaphylaxis and Other Allergic Reactions

Anaphylactic and other allergic reactions; rarely fatal.

Major Toxicities

Water Intoxication

Dose-related, severe water intoxication (due to oxytocin’s antidiuretic effect) with seizures, coma, and death following prolonged IV infusion of oxytocin with an excessive volume of fluid. Neonatal seizures also reported. Usually, only after prolonged administration of ≥40 milliunits/minute.

Consider potential for water intoxication, particularly when administered by IV infusion and patient is receiving oral fluids.

Restrict fluid intake, avoid administration of low-sodium infusion fluids and high oxytocin doses for prolonged periods, and monitor fluid intake and output during administration.

General Precautions

Monitoring

Qualified professional personnel with thorough knowledge and capability to identify complications of oxytocin should observe patient continuously, and a clinician qualified to manage complications should be immediately available.

Continuously monitor uterine contractions, fetal and maternal heart rate, maternal blood pressure, and, if possible, intrauterine pressure to avoid complications.

Carefully control delivery to minimize risk of increased postpartum bleeding (may be related to oxytocin-induced thrombocytopenia, afibrinogenemia, and hypoprothrombinemia).

Electronic monitoring of the fetus is the best method for early detection of overdosage, but accurate measurement of intrauterine pressure during contractions requires intrauterine pressure recording.

Determination of fetal heart rate via a fetal scalp electrode is more dependable than via external monitoring.

Uterine Hyperactivity

Inappropriate administration (e.g., excessive dosage) or with abortifacients or to sensitive patients may cause hyperstimulation of the uterus hazardous to mother and fetus.

Strong (hypertonic) and/or prolonged (tetanic) contractions, or a resting uterine tone of 15–20 mm H₂O between contractions may result.

Uterine rupture, cervical and vaginal lacerations, postpartum hemorrhage, abruptio placentae, impaired uterine blood flow, amniotic fluid embolism, and fetal trauma including intracranial hemorrhage may occur.

Discontinue immediately if uterine hyperactivity occurs; oxytocin-induced stimulation of uterine contractions usually decreases soon after discontinuance of the drug.

Complications of Pregnancy

Do not administer oxytocin when pregnancy is complicated by fetal distress, hydramnios, partial placenta previa, prematurity, borderline cephalopelvic disproportion, predisposition for uterine rupture (e.g., previous major surgery of the cervix or uterus including cesarean section, overdistension of the uterus, grand multiparity, history of uterine sepsis or traumatic delivery), except in unusual circumstances requiring the clinician’s judgment.

Maternal and Fetal Mortality

Maternal death from hypertensive episodes and subarachnoid hemorhage has resulted from injudicious use of oxytocin; also, rupture of the uterus, and fetal deaths due to various causes have been associated with oxytocic drug use for labor induction or augmentation in first and second labor stages.

Patient Selection

Carefully select patient; evaluate pelvic adequacy, and both maternal and fetal condition before oxytocin use. Consider that hypertonic contractions may occur when uterus is hypersensitive to oxytocin, even when properly administered.

Do not administer for prolonged periods in severe toxemia.

In patients with valvular heart disease and those receiving spinal and epidural anesthesia, administration of large dosages may be particularly hazardous; severe decreases in maternal systolic and diastolic blood pressure, increases in heart rate, systemic venous return and cardiac output, and arrhythmia may occur.

Specific Populations

Pregnancy

Manufacturers state oxytocin is not indicated for use during the first or second trimester of pregnancy other than in relation to spontaneous or induced abortion.

Based on experience, chemical and pharmacologic properties, not expected to cause fetal abnormalities when used as indicated.

May cause nonteratogenic fetal adverse effects.

Lactation

May be distributed into milk. Caution.

Common Adverse Effects

Adverse effects usually are dose related.

Uterine hyperstimulation and subsequent fetal heart rate deceleration most common. (See Uterine Hyperactivity under General Precautions.)

Maternal nausea, vomiting, sinus bradycardia, premature ventricular complexes; probably related to labor and not the drug.

Neonatal hyperbilirubinemia, jaundice, retinal hemorrhage, low Apgar scores at 5 minutes.

Drug Interactions

Specific Drugs

Oxytocin Pharmacokinetics

Absorption

Onset

IV administration: uterine response is almost immediate.

IM injection: uterine response occurs within 3–5 minutes.

IV administration of 100–200 milliunits: contractions of myoepithelial tissue surrounding the alveoli of the breasts begin within a few minutes.

Duration

IV administration: uterine response subsides within 1 hour.

IM injection: uterine response subsides in 2–3 hours.

IV administration of 100–200 milliunits: contractions of myoepithelial tissue surrounding the alveoli of the breasts continue for 20 minutes.

Plasma Concentrations

IV infusion rates up to 6 milliunits/minute produce maternal oxytocin plasma concentrations comparable to those associated with spontaneous labor.

Distribution

Extent

Distributed throughout the extracellular fluid.

Crosses the placenta.

Distributes into milk, probably in small amounts.

Elimination

Metabolism

Rapidly metabolized in the liver and kidneys.

Elimination Route

Small amounts excreted in urine unchanged.

Half-life

About 3–5 minutes.

Stability

Storage

Parenteral

Injection

2–8°C; do not freeze. May expose to 15–25°C for up to 30 days, but then discard.

Compatibility

Parenteral

Reported incompatible with various drugs, dependent on several factors (e.g., drug concentration, resulting pH, temperature).

Solution CompatibilityHID

Drug Compatibility

Actions

• Exogenous oxytocin elicits all the pharmacologic responses of endogenous oxytocin.

• Indirectly stimulates contraction of uterine smooth muscle by increasing the sodium permeability of uterine myofibrils.

• Increases contraction amplitude and frequency, which tends to decrease cervical activity, produce dilation and effacement of the cervix, and transiently impede uterine blood flow; contractions produced by oxytocin at term are similar to those occurring during spontaneous labor.

• High estrogen concentrations lower the threshold for uterine response to oxytocin.

• Uterine response increases with the duration of pregnancy and is greater in labor than when not in labor; only very large doses elicit contractions in early pregnancy.

• Contracts myoepithelial cells surrounding the alveoli of the breasts, forcing milk from the alveoli into the larger ducts and facilitating milk ejection.

• Minimal antidiuretic activity relative to vasopressin; water intoxication possible at high doses and/or excessive electrolyte-free fluid.

• Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs as well as any concomitant illnesses.

• Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.

• Importance of informing patients of other important precautionary information. (See Cautions.)

Preparations

Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.

Please refer to the ASHP Drug Shortages Resource Center for information on shortages of one or more of these preparations.

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