SYNTOCINON

What it is

SYNTOCINON is oxytocin injection, a sterile aqueous solution containing synthetic oxytocin. SYNTOCINON is available in ampoules containing 5 IU in 1 mL and 10 IU in 1 mL. The injection solution is clear and colourless.

Approved indications —

Induction of labour — Inadequate uterine effort — Management of third stage of labour — Post-partum haemorrhage

Dosing overview

For induction or augmentation of labour, SYNTOCINON should only be administered as an intravenous infusion, preferably by means of a variable speed infusion pump or by drip infusion, with an initial infusion rate of 1–4 milliunits per minute. This rate may be gradually increased at intervals of not shorter than 20 minutes and increments of not more than 1–2 milliunits per minute, until a contraction pattern similar to that of normal labour is established. The recommended maximum rate is 20 milliunits per minute. For third stage of labour and puerperium, SYNTOCINON may be given as 5–10 IU by intramuscular injection or 5 IU by slow bolus intravenous injection. For caesarean section, SYNTOCINON is given as 5 IU by intravenous infusion or slow bolus intravenous injection after delivery of the foetus.

Key safety warnings

Administration of oxytocin at excessive doses results in uterine over-stimulation which may cause foetal distress, asphyxia and death, or may lead to hypertonicity, tetanic contractions or rupture of the uterus. The frequency and duration of contractions and foetal heart rate must be carefully monitored during oxytocin administration, the latter preferably by electronic means, and the infusion must be discontinued immediately in the event of uterine hyperactivity, foetal distress or foetal heart abnormalities. Water intoxication associated with maternal and neonatal hyponatraemia, which is potentially fatal, has been reported in cases where high doses of oxytocin have been administered together with large amounts of electrolyte-free fluid over a prolonged period of time. The weak anti-diuretic activity of oxytocin may be a contributing factor, but the major cause is the use of large amounts of electrolyte-free fluids. When SYNTOCINON is used for prevention or treatment of uterine haemorrhage, rapid intravenous bolus injection of oxytocin at high doses should be avoided, as it may cause acute short-lasting hypotension accompanied by flushing and reflex tachycardia. These rapid haemodynamic changes may result in myocardial ischaemia, particularly in patients with pre-existing cardiovascular disease. There have been reports of anaphylaxis following administration of oxytocin in women with a known latex allergy. Latex allergy or intolerance may be an important predisposing risk factor for anaphylaxis following oxytocin administration.

Contraindications

Foetal distress and any condition in which, for foetal or maternal reasons, spontaneous labour is inadvisable and/or vaginal delivery is contraindicated are contraindications. These include cephalo-pelvic disproportion, abnormal presentation, cord presentation or prolapse, excessive distension or impaired resistance of the uterus to rupture (for example, multiple pregnancy, polyhydramnios), parity greater than 4, elderly multiparae, grand multiparity and in the presence of uterine scar resulting from major surgery including previous caesarean section or other surgery involving the uterus. Severe toxaemia, predisposition to amniotic fluid embolism (foetal death-in-utero, abruptio placentae), hypertonic contractions, placenta praevia and vasa praevia, and placental abruption are also contraindicated, as is hypersensitivity to oxytocin or to any of the excipients in the formulation. SYNTOCINON must not be administered within 6 hours after vaginal prostaglandins have been given.

Regulatory history

SYNTOCINON oxytocin injection ampoules (5 IU and 10 IU strengths) were first registered on the Australian Register of Therapeutic Goods on 21 August 1991.