Full Prescribing Info
Oxytocin is a sterile aqueous solution of synthetic Oxytocin for intravenous infusion or intramuscular injection containing 0.5% of chlorbutol as a preservative. The drug is prepared synthetically to avoid possible contamination with vasopressin (ADH) and its antidiuretic and cardiovascular effects.
Pharmacology: Oxytocin acts primarily on uterine myofibril activity by increasing the permeability of the cell membranes to sodium ions, thus augmenting the number of contracting myofibrils, and thereby enabling the uterus to produce the necessary number of contractions. The effect depends on the uterine threshold of excitability. The pharmacological and clinical properties of Oxytocin are identical with naturally occurring oxytocin principle of the posterior lobe of the pituitary. Oxytocin injection does not contain amino acids characteristic of vasopressin, and therefore has fewer and less severe cardiovascular effects. Oxytocin when given in appropriate doses during pregnancy is capable of eliciting graded increase in uterine motility from a moderate increase in rate and force of spontaneous motor activity to sustained titanic contractions. Oxytocin is promptly effective after parenteral administration. Following intramuscular injection, the myotonic effect on the uterus appears in 3-7 minutes, and persists for 30-60 minutes. With intravenous injection, the uterine effect appears within one minute and is of more brief duration.
Important Notice: Oxytocin is indicated for the medical rather than the elective induction of labour. Available data and information are inadequate to define the benefit to risk considerations in the use of drug products for elective induction. Elective induction of labour is defined as the initiation of labour for the convenience in an individual with a term pregnancy who is free of medical indications for the initiation of labour.
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: Induction of labour in patients with a medical indication for the initiation of labour, such as Rh problems. Maternal diabetes, preeclampsia at or near term, when delivery is in the best interest of both mother and fetus or when membranes are prematurely ruptured and delivery is indicated.
Stimulation of reinforcement of labour, as in selective cases of uterine inertia.
As adjunctive therapy in the management of incomplete or inevitable abortion. In the first trimester, curettage is generally considered primary therapy.
In the 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 labour and to control postpartum bleeding or hemorrhage.
Dosage/Direction for Use
Dosage of Oxytocin is determined by uterine response. The following dosage information is based upon the various regimens and indications in general use.
Induction or stimulation of labour: Intravenous infusion (drip method) is the only acceptable method of administration for the induction or stimulation of the labour. Accurate control of the rate of infusion flow is essential. An infusion pump or other such device and frequent monitoring of strength of contractions and fetal heart rate are necessary for the safe administration of Oxytocin for the induction or stimulation of labour. If uterine contractions become too powerful the infusion can be abruptly stopped, and Oxytocin stimulation of the uterine musculature will soon wane.
An intravenous infusion of non-Oxytocin containing solution should be started. Physiologic electrolyte solution should be used except under unusual circumstances.
To prepare the usual solution for infusion, the contents of Oxytocin injection equivalent to 10 units are combined aseptically with 1000 mL of nonhydrating diluent. The combined solution, rotated in the infusion bottle to ensure thorough mixing contains 10 mU/mL. Add the container with diluted Oxytocin solution to the system through use of constant infusion pump or other such device, to control accurately the rate of infusion.
The initial dose should not be more than 1-2 mU/minute. The dose may be gradually increased in increments of no more than 1-2 mU/minute until a contraction pattern has been established, which is similar to normal labour.
The fetal heart rate, resting uterine tone, the frequency, duration, and force of contractions should be monitored.
The oxytocin infusion should be discontinued immediately in the event of uterine hyperactivity or fetal distress. Oxygen should be administered to the mother. A responsible physician must evaluate the mother and the fetus.
Control of postpartum uterine bleeding: Intravenous infusion (Drip method): To control postpartum bleeding, 10-40 units of Oxytocin may be added to 1000 mL of a non-hydrating diluent and run at a rate necessary to control uterine atony.
Intramuscular administration: 10 units of Oxytocin can be given after delivery of the placenta.
Treatment of Incomplete or inevitable abortion: Intravenous infusion with physiologic saline solution, 500 mL or 5% dextrose in physiologic saline solution to which 10 units of Oxytocin have been added should be infused at rate of 20-40 drops per minute.
Overdosage with Oxytocin depends essentially on uterine hyperactivity whether or not due to hypersensitivity to this agent. Hyperstimulation with strong (hypertonic) or prolonged (isotonic) contractions or a resting tone of 15-20 mm H2O or between contracts.
Antepartum use of Oxytocin is contraindicated in any one of the following circumstances: When there is significant cephalopelvic disproportion.
In unfavorable fetal positions, such as transverse lies, which are undeliverable with out conversion prior to delivery.
In obstetrical emergencies where benefit-to-risk ratio for either the fetus or the mother favors surgical intervention.
In fetal distress where delivery is not imminent.
Where adequate uterine activity fails to achieve satisfactory progress.
Where the uterus is already hyperactive or hypertonic.
In patients with hypersensitivity to the drug.
In induction or augmentation of labour in those cases where vaginal delivery is contraindicated, such as cord presentation of prolapse, total placental previa and vasa previa.
Oxytocin, when given for the induction of labour or augmentation of uterine activity, should be administered only by the intravenous route and with adequate medical supervision in a hospital.
Special Precautions
All patients receiving intravenous Oxytocin must be under continuous observation by trained personnel who have thorough knowledge of the drug and are qualified to identify complications. A physician qualified to manage any complications should be immediately available.
When properly administered, Oxytocin should stimulate uterine contractions, comparable to those seen in normal labour. 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. The physician, in exercising his judgment regarding patient selection must consider this fact.
Except in unusual circumstances, Oxytocin should not be administered in the following conditions; fetal distress, partial placenta previa, prematurity, borderline cephalopelvic disproportion and any condition in which there is a predisposition for uterine rupture such as major surgery on the cervix or uterus including caesarean section, over distention of uterus, grand multiparity or past history of uterine sepsis or of traumatic delivery. Because of the variability of the combinations of factors, which may be present in conditions listed above the definition of "unusual circumstances", must be left to the judgment of the physician. The decision must be made carefully by weighing the potential benefits, which Oxytocin can provide against the rare but definite potential for the drug to produce hyper tonicity or tetanic spasm.
Maternal deaths due to hypertensive episodes, subarachnoid hemorrhage, rupture of the uterus and fetal deaths due to various causes have been reported associated with the use of parenteral oxytocic drugs for induction of labour or for augmentation in the first and second stages of labour.
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.
When Oxytocin is used for induction reinforcement of already existent labour, patients should be carefully selected. Pelvic inadequacy may be considered and maternal and fetal conditions should be evaluated before use of the drug.
Adverse Reactions
The following adverse reactions have been reported in the mother: Anaphylactic reaction; Postpartum hemorrhage; Cardiac arrhythmia; Fatal afibrinogenemia; Nausea; Premature ventricular contractions; Pelvic hematoma; Excessive dosage or hypersensitivity to the drug may result in uterine hypotonicity, spasm, titanic contraction, or rupture of the uterus and extensive laceration of the soft tissues; Severe water intoxication with convulsions and coma has occurred associated with slow Oxytocin infusion over at 24 hours period. Maternal death due to Oxytocin induced water intoxication has also been reported.
The following adverse reactions have been reported in the fetus or infant: Due to induced uterine motility: Bradycardia; Premature ventricular contractions and other arrhythmias; Permanent CNS or brain damage; Fetal death.
Due to use of Oxytocin in mother: Low Apgar scores at five minutes; Neonatal jaundice; Neonatal hemorrhage.
Drug Interactions
Severe hypertension has been reported when Oxytocin was given 3 to 4 hours following prophylactic administration of a vasoconstrictor in conjunction with a caudal block anesthetic. Cyclopropane anesthesia may modify Oxytocin's cardiovascular effects, so as to produce unexpected results such as hypotension. Maternal sinus bradycardia with abnormal atrioventricular rhythms have also been noted when Oxytocin was concomitantly administered with cyclopropane anesthesia.
Store at Temperatures between 2°C to 8°C.
Shelf-life: 24 months.
ATC Classification
H01BB02 - oxytocin ; Belongs to the class of oxytocin and analogues. Used in posterior pituitary lobe hormone preparations.
Inj (amp) 10 u/mL x 1 mL x 10's.
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