Oxytocin

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In Antepartum: Induction of labor in patients with a medical indication for the initiation of labor, such as Rh problems, maternal diabetes, (pre-) eclampsia at or near term, when delivery is in the best interests of mother and fetus or when membranes are prematurely ruptured and delivery is indicated;  ... Read moreIn Antepartum: Induction of labor in patients with a medical indication for the initiation of labor, such as Rh problems, maternal diabetes, (pre-) eclampsia at or near term, when delivery is in the best interests of mother and fetus or when membranes are prematurely ruptured and delivery is indicated;  Stimulation or reinforcement of labor, as in selected cases of uterine inertia; As adjunctive therapy in the management of incomplete or inevitable abortion.  In Postpartum: Oxytocin is indicated to produce uterine contractions during the third stage of labor and to control postpartum bleeding or hemorrhage.

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This drug is contraindicated in- significant cephalopelvic disproportion; unfavorable fetal positions or presentations which are undeliverable without conversion prior to delivery, e.g., transverse lies; in obstetrical emergencies where the benefit-to-risk ratio for either the fetus or the mother favors surgical intervention; in cases of fetal distress where delivery is not imminent; hypertonic uterine patterns; hypersensitivity to the drug. Prolonged use in uterine inertia or severe toxemia is contraindicated. Oxytocin should not be used in cases where vaginal delivery is not indicated.

Uterine motility depends on the formation of the contractile protein actomyosin under the influence of the Ca2+ dependent phosphorylating enzyme myosin light-chain kinase. Oxytocin promotes contractions by increasing the intracellular Ca2+, which in turn activates myosin's light chain kinase. Oxytocin has specific receptors in the muscle lining of the uterus and the receptor concentration increases greatly during pregnancy, reaching a maximum in early labor at term.

Severe hypertension has been reported when Oxytocin was given three to four hours following prophylactic administration of a vasoconstrictor in conjunction with caudal-block anesthesia. Cyclopropane anesthesia may modify Oxytocin’s cardiovascular effects, so as to produce unexpected results such as hypotension. Maternal sinus bradycardia with abnormal atrioventricular rhythms has also been noted when Oxytocin was used concomitantly with cyclopropane anesthesia.

Hypersensitivity to the drug may result in uterine hypertonicity, spasm, titanic contraction or rupture of the uterus.  The possibility of increased blood loss and afbrinigenemia should be kept in mind when administering the drug. Severe water intoxication with convulsions and coma has occurred.  Oxytocin may occasionally cause nausea, vomiting, haemorrhage or cardiac arrhythmias, anaphylactic reaction.

Overdosage with Oxytocin depends essentially on uterine hyperactivity whether or not due to hypersensitivity to this agent. Hyperstimulation with strong (hypertonic) or prolonged (tetanic) contractions, or a resting tone of 15 to 20 mm H2O or more between contractions can lead to tumultuous labor, uterine rupture, cervical and vaginal lacerations, postpartum hemorrhage, utero-placental hypoperfusion, and variable deceleration of fetal heart, fetal hypoxia, hypercapnia, or death. Water intoxication with convulsions, which is caused by the inherent antidiuretic effect of Oxytocin, is a serious complication that may occur if large doses (40 to 50 mU/minute) are infused for long periods. Management consists of immediate discontinuation of Oxytocin and symptomatic and supportive therapy.

Pregnancy category C. It is not known whether Oxytocin is excreted in human milk

Oxytocin should not be administered in the following conditions: prematurity, borderline cephalopelvic disproportion, previous major surgery on the cervix or uterus including caesarean section, overdistention of the uterus, grand multiparity or invasive cervical carcinoma.