Oxytocin

OXYTOCIN- oxytocin injection
Hikma Pharmaceuticals USA Inc.

FOR INTRAVENOUS INFUSION OR INTRAMUSCULAR USE

Rx only

DESCRIPTION

Each mL of Oxytocin Injection sterile solution contains an oxytocic activity equivalent to 10 USP Posterior Pituitary Units, Chlorobutanol (a chloroform derivative), 0.5%, as a preservative, and acetic acid to adjust pH (3.0 to 5.0). Oxytocin is intended for IM or IV use. Oxytocin is a synthetic polypeptide; it occurs as a white powder and is soluble in water. It may be designated chemically as:

Structural formula
(click image for full-size original)

CLINICAL PHARMACOLOGY

The pharmacologic and clinical properties of oxytocin are identical with those of naturally occurring oxytocin principle of the posterior lobe of pituitary. Oxytocin exerts a selective action on the smooth musculature of the uterus, particularly toward the end of pregnancy, during labor, and immediately following delivery. Oxytocin stimulates rhythmic contractions of the uterus, increases the frequency of existing contractions, and raises the tone of the uterine musculature.

When given in appropriate doses during pregnancy, oxytocin is capable of eliciting graded increases in uterine motility from a moderate increase in the rate and force of spontaneous motor activity to sustained titanic contraction. The sensitivity of the uterus to oxytocic activity increases progressively throughout pregnancy until term when it is maximal.

Oxytocin is distributed throughout the extracellular fluid. Small amounts of this drug probably reach the fetal circulation. Oxytocin has a plasma half-life of about 3 to 5 minutes. Following parenteral administration, uterine response occurs within 3 to 5 minutes and persists for 2 to 3 hours. Its rapid removal from plasma is accomplished largely by the kidney and the liver. Only small amounts oxytocin are excreted in the urine unchanged.

INDICATIONS AND USAGE

IMPORTANT NOTICE
Oxytocin is indicated for the medical rather than the elective induction of labor. Available data and information are inadequate to define the benefits-to-risks considerations in the use of the drug product for elective induction. Elective induction of labor is defined as the initiation of labor for convenience in an individual with a term pregnancy who is free of medical indications.

Antepartum

Oxytocin is indicated for the initiation or improvement of uterine contractions, where this is desirable and considered suitable for reasons of fetal or maternal concern, in order to achieve early vaginal delivery. It is indicated for (1) induction of labor in patients with a medical indication for the initiation of labor, such as Rh problems, maternal diabetes, preeclampsia 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; (2) stimulation or reinforcement of labor, as in selected cases of uterine inertia; (3) as adjunctive therapy in the management of incomplete or inevitable abortion. In the first trimester, curettage is generally considered primary therapy. In second trimester abortion, oxytocin infusion will often be successful in emptying the uterus. Other means of therapy, however, may be required in such cases.

Postpartum

Oxytocin is indicated to produce uterine contractions during the third stage of labor and to control postpartum bleeding or hemorrhage.

CONTRAINDICATIONS

Oxytocin is contraindicated in any of the following conditions:

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, such as cord presentation or prolapse, total placenta previa, and vasa previa.

WARNINGS

Oxytocin, when given for induction or stimulation of labor, must be administered only by intravenous infusion (drip method) and with adequate medical supervision in a hospital.

PRECAUTIONS

General

  1. All patients receiving intravenous infusions of oxytocin must be under continuous observation by trained personnel with a thorough knowledge of the drug and are qualified to identify complications. A physician qualified to manage any complications should be immediately available.
  2. When properly administered, oxytocin should stimulate uterine contractions similar to those seen in normal labor. Overstimulation of the uterus by improper administration can be hazardous to both mother and fetus. Even with proper administration and adequate supervision, hypertonic contractions can occur in patients whose uteri are hypersensitive to oxytocin.
  3. Except in unusual circumstances, oxytocin should not be administered in the following conditions: prematurity, borderline cephalopelvic disproportion, previous major surgery on the cervix or uterus, including cesarean section, overdistention of the uterus, grand multiparity, or invasive cervical carcinoma. Because of the variability of the combinations of factors which may be present in the conditions listed above, the definition of “unusual circumstances” must be left to the judgment of the physician. The decision can only be made by carefully weighing the potential benefits which oxytocin can provide in a given case against the rare occurrence of hypertonicity or tetanic spasm with this drug.
  4. Maternal deaths due to hypertensive episodes, subarachnoid hemorrhage, rupture of the uterus, and fetal deaths and permanent CNS or brain damage of the infant due to various causes have been reported to be associated with the use of parenteral oxytocic drugs for induction of labor or for augmentation in the first and second stages of labor.
  5. Oxytocin has been shown to have an intrinsic antidiuretic effect, acting to increase water reabsorption from the glomerular filtrate. Consideration should, therefore, be given to the possibility of water intoxication, particularly when oxytocin is administered continuously by infusion and the patient is receiving fluids by mouth.
  6. Oxytocin should be considered for use only in patients who have been carefully selected. Pelvic adequacy must be considered and maternal and fetal conditions thoroughly evaluated before use of the drug.

Drug Interactions

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.

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