Oxytocin

Pronunciation: ox-ih-TOE-sin
Class: Uterine-active agents

Trade Names

Pitocin
- Injection 10 units/mL

Pharmacology

Endogenous hormone with uterine stimulant properties and vasopressive and antidiuretic effects.

Slideshow: Top 10 Ways to Save on Your Medication Costs

Pharmacokinetics

Distribution

Distributed throughout the extracellular fluid. Small amounts may reach fetal circulation.

Elimination

Small amounts are unchanged in the urine. The t _½ of plasma is 1 to 6 min.

Onset

Onset of uterine contraction occurs almost immediately in the IV form. In the IM form, it occurs between 3 to 5 min.

Duration

IM is 2 to 3 h. IV is 1 h.

Indications and Usage

Initiation or improvement of uterine contractions to achieve early vaginal delivery for maternal or fetal reasons (IV); as adjunctive therapy in the management of inevitable or incomplete abortion (IV); stimulation of uterine contractions during third stage of labor (IV); stimulation reinforcement of labor, as in selected cases of uterine inertia (IV); control of postpartum bleeding or hemorrhage (IV, IM); induction of labor in patients with a medical indication for the initiation of labor (eg, Rh problems, maternal diabetes, preeclampsia at or near term) when in the best interest of mother and fetus or when membranes are prematurely ruptured and delivery is indicated (IV).

Contraindications

Hypersensitivity to the drug; significant cephalopelvic disproportion; inadequate, undeliverable fetal position; obstetric emergencies in which surgical intervention is preferred; cases of fetal distress in which delivery is not imminent; prolonged use in uterine inertia or severe toxemia; hypertonic or hyperactive uterine patterns; when adequate uterine activity fails to achieve satisfactory response; when vaginal delivery is contraindicated (eg, invasive cervical carcinoma, active herpes genitalis, total placenta previa, vasa previa, prolapse of the cord).

Dosage and Administration

IV infusion (drip method) or IV 0.5 to 2 milliunits/min; adjust by no more than 1 to 2 milliunits/min at 30- to 60-min intervals until contraction pattern similar to normal labor is obtained. Once the desired frequency of contractions has been reached, the dose may be reduced by similar increments.

IV infusion 10 to 20 milliunits/min (max, 30 units in 12 h).

IV infusion (drip method) 10 to 40 units in 1,000 mL diluent to run as infusion at rate necessary to control uterine atony. IM 10 units (1 mL) after delivery of placenta.

General Advice

• Induction or Stimulation of Labor
• Administer by IV infusion only. Not for intradermal, subcutaneous, IM, IV bolus, or intra-arterial administration in this situation.
• For IV infusion add 1 mL (10 units) of oxytocin to 1,000 mL sodium chloride 0.9% injection or Ringer's lactate to produce solution containing 10 milliunits/mL (0.01 units/mL). Rotate infusion bottle to ensure thorough mixing. Administer via constant infusion pump to accurately control rate of infusion.
• Piggy-back oxytocin infusion on a physiologic electrolyte solution (eg, sodium chloride 0.9% injection).

• Control of Postpartum Uterine Bleeding
• Administer by IM injection or IV infusion only. Not for intradermal, subcutaneous, IV bolus, or intra-arterial administration in this situation.
• For IV infusion add 10 to 40 units (1 to 4 mL) of oxytocin to patient's IV infusion solution as ordered (do not exceed 40 units in 1,000 mL). Adjust infusion rate to sustain uterine contraction and control uterine atony.
• For IM administration, inject 10 units (1 mL) after delivery of placenta as ordered.

• Treatment of Incomplete, Inevitable, or Elective Abortion
• Administer by IV infusion only. Not for intradermal, subcutaneous, IM, IV bolus, or intra-arterial administration in this situation.
• For IV infusion add 10 units (1 mL) of oxytocin to 500 mL of physiologic saline solution or dextrose 5%-in-water solution.

Storage/Stability

Store in refrigerator (36° to 46°F). May store at controlled room temperature (59° to 77°F) for up to 30 days. Discard after 30 days if stored at room temperature.

Drug Interactions

May cause maternal hypotension, bradycardia, and abnormal AV rhythms.

Severe hypertension occurred when oxytocin was given 3 to 4 h following prophylactic administration of a vasoconstrictor in conjunction with caudal block anesthesia.

Incompatibility

Sodium bicarbonate. Oxytocin is rapidly decomposed in the presence of sodium bisulfite.

Laboratory Test Interactions

None well documented.

Adverse Reactions

Cardiovascular

Maternal reactions include cardiac arrhythmias, premature ventricular contractions, hypertensive episodes; fetal or neonatal reactions include bradycardia, premature ventricular contractions, other arrhythmias.

CNS

Fetal or neonatal reactions include permanent CNS or brain damage and seizures.

EENT

Fetal or neonatal reactions include retinal hemorrhage.

GI

Maternal reactions include nausea and vomiting.

Genitourinary

Maternal reactions include rupture of uterus, uterine hypertonicity.

Hepatic

Fetal or neonatal reactions include jaundice.

Metabolic-Nutritional

Maternal reactions include severe water intoxication with convulsion, coma, and death.

Miscellaneous

Maternal reactions include anaphylactic reaction, fatal absence of fibrinogen in the plasma, pelvic hematoma, postpartum hemorrhage, subarachnoid hemorrhage; fetal and neonatal reactions include death, low Apgar scores at 5 min.

Precautions

Pregnancy

No indication for use in first trimester unless related to spontaneous or induced abortion.

Lactation

Undetermined.

Special Risk Patients

Not recommended in prematurity, borderline cephalopelvic disproportion, previous major surgery on cervix or uterus (including cesarean section), uterine over-distention, grand multiparity, history of uterine sepsis, traumatic delivery, fetal distress, hydramnios, partial placenta previa, or invasive cervical carcinoma, except in unusual circumstances.

Mortality

Hypertensive episodes, subarachnoid hemorrhage, and rupture of uterus have resulted in maternal deaths. Fetal deaths and infant brain damage have been reported with IV use during first and second stages of labor.

Overstimulation of uterus

Overstimulation of uterus can occur and can be hazardous to mother and fetus.

Water intoxication

Consider possibility when patient is receiving oxytocin by IV infusion and fluids by mouth.

Overdosage

Symptoms

Uterine hyperactivity (hyperstimulation with hypertonic or tetanic contractions), uterine rupture, cervical and vaginal lacerations, postpartum hemorrhage, uteroplacental hypoperfusion, variable deceleration of fetal heart, fetal hypoxia, hypercapnia, perinatal hepatic necrosis, death, water intoxication with seizures.

Patient Information

• Advise patient and family that medication will be prepared and administered by a health care provider in a medical setting with very close monitoring of the effects of the medication.

Copyright © 2009 Wolters Kluwer Health.