Oxytocin

Intravenous
Postpartum haemorrhage

Intravenous
Adjunct in abortion

Intravenous
Labour induction

Intravenous
Oxytocin challenge test for evaluating of fetal distress

Nasal
Facilitate lactation

Intravenous:
Postpartum haemorrhage: Postpartum uterine bleeding: oxytocin 10-40 units to running IV infusion, max 40 units/1000 ml.
Adjunct in abortion: Oxytocin 10 units to 500 ml of a physiologic saline solution or glucose 5%.
Labour induction: Oxytocin 10 units to 500-1000 ml normal saline or lactated Ringer's to produce a solution of 10 milliunits/ml, rotate solution to mix. Normally infused at 3 ml/hr (delivering 0.001 unit/min). For higher doses: oxytocin 30 units can be added to 500 ml of diluent and infused at 1 ml/hr (delivering 0.001 unit/min).

Intravenous:
Postpartum haemorrhage: When admixed: fibrinolysin (human), norepinephrine, prochlorperazine edisylate, warfarin; variable compatibility with phytonadione.
Adjunct in abortion: When admixed: fibrinolysin (human), norepinephrine, prochlorperazine edisylate, warfarin; variable compatibility with phytonadione.
Labour induction: When admixed: fibrinolysin (human), norepinephrine, prochlorperazine edisylate, warfarin; variable compatibility with phytonadione.
Nasal:
When admixed: fibrinolysin (human), norepinephrine, prochlorperazine edisylate, warfarin; variable compatibility with phytonadione.

Cephalopelvic disproportion; abnormal presentation of the foetus; hydraminios; multiparae; previous caesarian section or other uterine surgery; hyperactive or hypertonic uterus, uterine rupture; contraindicated vaginal delivery (invasive cervical cancer, active genital herpes, prolapse of the cord, cord presentation, total placenta previa or vasa previa); foetal distress where delivery is not imminent; severe pre-eclamptic toxaemia.

CV disorders; >35 yr; lactation. Monitor foetal and maternal heart rate, maternal BP and uterine motility. Monitor fluid intake and output during treatment. Discontinute immediately if the uterus is hypertonic or hyperactive or if there is foetal distress. Use of nasal spray may produce maternal dependence on its effects. IM admin not regularly used due to unpredictable effects of oxytocin. Not to be used for prolonged periods in resistant uterine inertia, severe pre-eclampsia, or severe CV disorders. Risk of water intoxication when used at high doses for prolonged periods.

Foetus or neonate: Jaundice; arrhythmias, bradycardia; brain, CNS damage; seizure; retinal haemorrhage; low Apgar score. Mother: transient hypotension, reflex tachycardia; nasal irritation, rhinorrhoea, lachrymation (following nasal admin); uterine bleeding, violent contractions, hypertonicity; spasm; nausea, vomiting.
Potentially Fatal: Maternal water intoxication (especially with slow infusion over 24 hr); prolonged uterine contractions causing foetal hypoxia and death; rupture of gravid uterus; afibrinogenaemia; subarachnoid haemorrhage

IM/IV/Parenteral: C

Tetanic uterine contractions, impaired uterine blood flow, amniotic fluid embolism, uterine rupture, syndrome of inappropriate antidiuretic hormone secretion and seizures. Treatment: Supportive and symptom specific.

Possible severe hypertension if given within 3-4 hr of vasoconstrictor in association with a caudal block anaesthesia. Cyclopropane anaesthesia may increase risk of hypotension and maternal sinus bradycardia with abnormal AV rhythms. Dinoprostone and misoprostol may increase uterotonic effect of oxytocin, thus oxytocin should not be used within 6 hr after admin of vaginal prostaglandins. Concurrent use may increase the vasopressor effect of sympathomimetics.
Potentially Fatal: Concomitant use with prostaglandins increases risk of uterine rupture and cervical lacerations.

Description: Oxytocin induces rhythmic uterine contraction which increases throughout the pregnancy, reaching the max at term by proliferating oxytocin receptors. It increases the tone and amplitude of the uterine contractions at small doses.
Onset: Uterine contractions: IM: 3-5 minutes; IV: approx 1 minute.
Duration: IM: 2-3 hr; IV: 1 hr.
Pharmacokinetics:
Absorption: Steady state is reached normally 40 minutes after parenteral admin.
Distribution: Distribution throughout extracellular fluid, small amounts reach foetus.
Metabolism: Rapidly via the liver and plasma (by oxytocinase); some metabolism via mammary gland.
Excretion: Elimination half-life: 1-5 minutes; excreted via urine.

Store at 2-8 °C.

Drugs Acting on the Uterus