OXYTOCINE INJECTION BP
OXYTOCIN INJECTION BP is available in ampoules containing 3 IU (5.00 µg/ml Oxytocin BP with an activity of 600 units per mg) and 10 IU/ml of 600 units per mg), 5 IU/ml (8.33µg/ml) and 10 IU/ml (16.66 µg/m/). Other ingredients: Sodium chloride, acetic acid, sodium acetate, Water for injections.
The active principle of OXYTOCIN INJECTION BP is a synthetic nonapeptide identical with Oxytocin, a hormone released by the posterior lobe of the pituitary. It exerts a stimulatory effect on the smooth musculature of the uterus, particularly towards the end of pregnancy, during labour, after delivery, and in the puerperium, i.e. at times when the number of specific oxytocin receptors in the myometrium is increased.
When given by low-dose intravenous infusion, OXYTOCIN INJECTION BP elicits rhythmic uterine contractions that are indistinguishable in frequency, force, and duration from those observed during spontaneous labour. At higher infusion dosages, or when given by single injection, the drug is capable of causing sustained uterine contractions.
Being synthetic, OXYTOCIN INJECTION BP does not contain vasopressin, but even in its pure form oxytocin possesses some weak intrinsic vasopressin-like antidiuretic activity. Another pharmacoIogical effect observed with high doses of oxytocin, particularly when administered by rapid intravenous bolus injection, consists in a transient direct relaxing effect on vascular smooth muscle, resulting in brief hypotension, flushing, and reflex tachycardia.
OXYTOCIN INJECTION BP may be used for: Induction of labour for medical reasons; stimulation of labour in hypotonic uterine inertia; during caesarian section following the delivery of the child; prevention and treatment of postpartum uterine atony and haemorrhage. OXYTOCIN INJECTION BP may also be indicated in early stages of pregnancy as an adjunctive therapy for the management of incomplete, inevitable or missed abortion.
Dosage and administration
Induction or enhancement of labour
OXYTOCIN INJECTION BP should be administered as an intravenous drip infusion or, preferably, by means of a variable-speed infusion pump. For drip infusion it is recommended that 10 IU of OXYTOCIN INJECTION BP be added to 1/ of a physiologic electrolyte solution. For patients in whom infusion of sodium chloride must be avoided, 5% dextrose solution may be used as the diluent (see ‘Precautions’). To ensure even mixing, the bottle or bag must be turned upside down several times before use. The initial infusion rate should be set at 1- 4 mU/min (2-8 drops/min) It may be gradually increased at intervals not shorter than 20 min, until a contraction pattern similar to that of normal labour is established. In pregnancy near term this can often be achieved with an infusion of less than 10 mU/min (20 drops/min), and the recommended maximum rate is 20 mU/min (40 drops/min). In the unusual event that higher rates are required, as may occur in the management of foetal death in utero or for induction of labour at an earlier stage of pregnancy, when the uterus is less sensitive to oxytocin, it is advisable to use a more concentrated OXYTOCIN INJECTION BP solution, e.g. 10 IU in 500 ml.
When using a motor-driven infusion pump which delivers smaller volumes than those given by drip infusion, the concentration suitable for infusion within the recommended dosage range must be calculated according to the specifications of the pump.
The frequency, strength, and duration of contractions as well as the foetal heart rate must be carefully monitored throughout the infusion. Once an adequate level of uterine activity is attained, the infusion rate can often be reduced. In the event of uterine hyperactivity and/or foetal distress,the infusion must be discontinued
If, in women who are at term or near term, regular contractions are not established after the infusion of a total amount of 5 IU, it is recommended that the attempt to induce labour be ceased; it may be repeated on the following day, starting again from a rate of 1-4 mU/min.
5 IU by slow intravenous injection immediately after delivery.
Prevention of postpartum Uterine haemorrhage
The usual dose is 5 IU slowly i.v. after delivery of the placenta. In women given OXYTOCIN INJECTION BP for induction or enhancement of labour, the infusion should be continued at an increased rate during the third stage of labour and for the next few hours thereafter.
Treatment of postpartum uterine haemorrhage
5- 10 IU i.m. or 5 IU slowly i.v., followed in severe cases by intravenous infusion of a solution containing 5-20 IU of oxytocin in 500 ml of a non-hydrating diluent, run at the rate necessary to control uterine atony.
Incomplete, inevitable, or missed abortion
5 IU i.m. or slowly i.v., if necessary followed by intravenous infusion at a rate of 20-40 mU/min or higher.
Contraindications, warnings, etc.
Hypersensitivitv to the drug, Hypertonic uterine contractions, mechanical obstruction to delivery, foetal distress. Any condition in which for foetal or maternal reasons spontaneous labour is inadvisable and/or vaginal delivery is contraindicated: e.g. significant cephalopelvic disproportion, foetal malpresentation; placenta praevia and vasa praeyia, placental abruption, cord presentation or prolapse, overdistension or impaired resistance of the uterus to rupture as in multiple pregnancy, polyhydramnios, grand multiparity and in the presence of a uterine scar resulting from major surgery including classical caesarean section.
OXYTOCIN LNJECTION BP should not be used for prolonged periods in patients with oxytocinresistant uterine inertia, severe pre-eclamptic toxaemia or severe cardiovascular disorders.
The induction of labour by means of oxytocin should be attempted only when strictly indicated for medical reasons. Administration should only be under hospital conditions and qualified medical supervision. When given for induction and enhancement of labour, OXYTOCIN INJECTION BP must only be administered as an intravenous infusion and never by intravenous bolus injection. Careful monitoring of foetal heart rate and uterine motility (frequency, strength, and duration of contractions) is essential, so that the dosage may be adjusted to individual response.
When OXYTOCIN INJECTION BP, is given for induction or enhancement of labour particular caution is required in the presence of borderline cephalopelvic disproportion, secondary uterine inertia, mild to moderate degrees of pregnancy-induced hypertension or cardiac disease and in patients above 35 years of age or with a history of lower-uterine-segment caesarean sections.
In the case of foetal death in utero, and/or in the presence of meconium-stained amniotic fluid, tumultuous labour must be avoided, as it may cause amniotic fluid embolism.
Because oxytocin possesses slight antidiuretic activity, its prolonged intravenous administration at high doses in conjunction with large volumes of fluid, as may be be the case in the treatment of inevitable or missed abortion, or in the management of postpartum haemorrhage, may cause water intoxication associated with hyponatraemia.
To avoid this rare complication, the following precautions must be observed whenever high doses of oxytocin are administered over a long time: an electrolyte-containing diluent must be used (not dextrose); the volume of infused fluid should be kept low (by infusing oxytocin at a higher concentration than recommended for the induction or enhancement of labour at term); fluid intake by mouth must be restricted; a fluid balance chart should be kept, and serum electrolytes should be measured when electrolyte imbalance is suspected.
When OXYTOCIN INJECTION BP, is used for prevention or treatment of uterine haemorrhage, rapid intravenous injection should be avoided, as it, may cause an acute short-lasting drop in blood pressure. Prostaglandins may potentiate the uterotonic effect of oxytocin and vice versa; therefore, concomitant administration requires very careful monitoring.
Some inhalation anaesthetics, e.g. cyclopropane or halothane, may enhance the hypotensive effect of oxytocin and reduce its oxytocic action. Their concurrent use with oxytocin has also been reported to cause cardiac rhythm disturbances.
When given during or after caudal block anaesthesia, oxytocin may potentiate the pressor effect of sympathomimetic vasoconstrictor agents.
The fatal dose of OXYTOCIN INJECTION BP has not been established. OXYTOCIN INJECTION BP is subject to inactivation by proteolytic enzymes of the alimentary tract. Hence it is not absorbed from the intestine and is not likely to have toxic effects when ingested. The symptoms and consequences of overdosage are those mentioned under ‘Side-effects’. Ln addition, as a result of uterine overstimulation, placental abruption and/or amniotic fluid embolism have been reported.
When signs or symptoms of overdosage occur during continuous i.v. administration of OXYTOCIN INJECTION BP, the infusion must be discontinued at once and oxygen should be given to the mother. In cases of water intoxication it is essential to restrict fluid intake, promote diuresis, correct electrolyte imbalance, and control convulsions that may eventually occur, by judicious use of diazepam. In the case of coma, a free airway shoud be maintained with routine measures normally employed in the nursing of the unconscious patient.
As there is a wide variation in uterine sensitivity, uterine spasm may be caused in some instances by what are normally considered to be low doses.
When OXYTOCIN INJECTION BP is used by i.v. infusion for the induction or enhancement of labour, its administration at too high doses results in uterine overstimulation which may cause foetal distress, asphyxia, and death, or may lead to hypertonicity, tetanic contractions, soft tissue damage or rupture of the uterus.
Water intoxication associated with maternal and neonatal hyponatraemia has been reported in cases where high doses of oxytocin together with large amounts of electrolyte-free fluid have been administered over a prolonged period of time (see ‘Precautions’). Symptoms of water intoxication include:
1. Headache, anorexia, nausea, vomiting and abdominal pain.
2. Lethargy, drowsiness, unconsciousness and grandmal type seizures.
3. Low blood electrolyte concentration.
Rapid intravenous bolus injection of oxytocin at doses amounting to several IU may result in acute short-lasting hypotension accompanied with flushing and reflex tachycardia.
Oxytocin may occasionally cause nausea, vomiting, or cardiac arrhythmias. In a few cases, skin rashes and anaphylactoid reactions associated with dyspnoea, hypotension, or shock have been reported.
Store between +2 oC and +8 oC. Do not freeze. Any portion of the contents remaining should be discarded. OXYTOCN INJECTION BP should not be infused via the same apparatus as blood or plasma, because the peptide linkages are rapidly inactivated by oxytocin-inactivating enzymes.
OXYTOCIN INJECTION BP is incompatible with solutions containing sodium metabisulphite as a stabiliser.
OXYTOCIN INJECTION BP is compatible with the following infusion fluids, but due attention should be paid to the advisability of using electrolyte fluids in individual patients: Dextrose 5%, Sodium/potassium chloride (103 mmol Na+ and 51 mmol K+), Laevulose 20%, Macrodex 6%, Sodium bicarbonate 1.39%, Sodium chloride 0.9%, Sodium lactate 1.72%, Rheomacrodex 10%, Ringer’s solution.
Date of Issue: December 2000.