Oxytocin, parenteral
Oxytocin, parenteral (Pitocin)
Oxytocin, parenteral
(ox-eh- TOE-sin)
Pregnancy Category: X Pitocin (Rx)

Classification: Oxytocic agent

Action/Kinetics: Synthetic compound identical to the natural hormone isolated from the posterior pituitary. Has uterine stimulant, vasopressor, and weak antidiuretic properties. May act on uterine myofibril activity to increase the number of contracting myofibrils. Uterine sensitivity to oxytocin, as well as amplitude and duration of uterine contractions, increases gradually during gestation and just before parturition increases rapidly. Facilitates ejection of milk from the breasts by stimulating smooth muscle. Onset, IV: immediate; IM, 3-5 min; Peak effects: 40 min. Steady-state plasma levels: Reached within 40 min. t 1/2: 1-6 min (decreased in late pregnancy and lactation). Duration, IV: 20 min after infusion is stopped; IM: 2-3 hr. Eliminated through the urine, liver, and functional mammary gland.

Uses: Antepartum: Induction or stimulation of labor at term. To overcome true primary or secondary uterine inertia. Induction of labor with oxytocin is indicated only under certain specific conditions and is not usual because serious toxic effects can occur.
Oxytocin is indicated:

1. For uterine inertia.

2. For induction of labor in cases of erythroblastosis fetalis, maternal diabetes mellitus, preeclampsia, and eclampsia.

3. For induction of labor after premature rupture of membranes in last month of pregnancy when labor fails to develop spontaneously within 12 hr.

4. For routine control of postpartum hemorrhage and uterine atony.

5. To hasten uterine involution.

6. To complete inevitable abortions after the 20th week of pregnancy.

7. Intranasally for initial letdown of milk.

Investigational: Breast engorgement, oxytocin challenge test for determining antepartum fetal HR.

Contraindications: Hypersensitivity to drug. Significant cephalopelvic disproportion; unfavorable fetal positions or presentations that are undeliverable without conversion prior to delivery. In obstetric emergencies where the benefit-to-risk ratio for either the mother or fetus favors surgical intervention. Fetal distress where delivery is not imminent, prolonged use in uterine inertia or severe toxemia, hypertonic or hyperactive uterine patterns, when adequate uterine activity does not achieve satisfactory progress. Induction of augmentation of labor where vaginal delivery is contraindicated, including invasive cervical cancer, cord presentation or prolapse, total placenta previa and vasa previa, active herpes genitalis. Use of oxytocin citrate in severe toxemia, CV or renal disease. Use of intranasal oxytocin during pregnancy.
Also, predisposition to thromboplastin and amniotic fluid embolism (dead fetus, abruptio placentae), history of previous traumatic deliveries, or women with four or more deliveries. Never give oxytocin IV undiluted or in high concentrations.

Side Effects: Mother: Tetanic uterine contractions, anaphylaxis cardiac arrhythmia, fatal afibrinogenemia N&V, PVCs, increased blood loss, pelvic hematoma, hypertension, tachycardia, and ECG changes. Also, rarely, anxiety, dyspnea, precordial pain, edema, cyanosis or reddening of the skin, and CV spasm. Water intoxication from prolonged IV infusion, death due to hypertensive episodes, SAH, postpartum hemorrhage, or uterine rupture. Excessive dosage may cause uterine hypertonicity, spasm, tetanic contraction, or uterine rupture.
Fetus: Death PVCs, bradycardia, tachycardia, arrhythmias, hypoxia, intracranial hemorrhage due to overstimulation of the uterus during labor leads to uterine tetany with marked impairment of uteroplacental blood flow.

NOTE: Hypersensitivity reactions occur rarely. When they do, they occur most often with natural oxytocin administered IM or in concentrated IV doses and least frequently after IV infusion or diluted doses. Accidental swallowing of buccal tablets is not harmful.

Overdose Mangement: Symptoms: Hyperstimulation of the uterus resulting in hypertonic or tetanic contractions. Or, a resting tone of 15-20 cm water between contractions can result in uterine rupture, cervical and vaginal lacerations, tumultuous labor, uteroplacental hypoperfusion, postpartum hemorrhage, and a variable deceleration of fetal heart rate, fetal hypoxia, hypercapnia, or death. Water intoxication with seizures can occur if large doses (40-50 mL/min) of the drug are infused for long periods of time. Treatment: Discontinue the drug and restrict fluid intake. Start diuresis and give a hypertonic saline solution IV. Correct electrolyte imbalance and control seizures with a barbiturate. If the client is comatose, provide special nursing care.

Drug Interactions: Cyclopropane / Hypotension; also, maternal sinus bradycardia with abnormal AV rhythms Sympathomimetic amines / Severe hypertension and possible stroke

How Supplied: Injection: 10 U/mL.

Dosage
•IV Infusion, IM Induction or stimulation of labor.
Dilute 10 units (1 mL) to 1,000 mL isotonic saline or 5% dextrose for IV infusion. Initial: 0.001-0.002 unit/min (0.1-0.2 mL/min); dose can be gradually increased at 15- to 30-min intervals by 0.001 unit/min (0.1 mL/min) to maximum of 0.02 unit/min (2 mL/min).
Reduction of postpartum bleeding.
Dilute 10-40 units (1-4 mL) to 1,000 mL with isotonic saline or 5% dextrose for IV infusion. Administer at a rate to control uterine atony, usually at a rate of 0.02-0.1 unit/min.
Incomplete or therapeutic abortion.
10 units at a rate of 0.02-0.04 unit/min by IV infusion or 10 units IM after placental delivery.