Oxytocin

Indications

Oxytocin is used for: Postpartum haemorrhage, Labour induction, Abortion, Facilitate lactation

Adult Dose

Intravenous Adult: Postpartum Hemorrhage 10-40 units; not to exceed 40 units; to 1000 mL of nonhydrating IV solution and infuse at necessary rate to control uterine atony Labor Induction 0.5-1 mUnit/min IV, titrate 1-2 mUnit/min q15-60min until contraction pattern reached that is similiar to normal labor (usually 6 mUnits/min); may decrease dose after desired frequency of contraction reached and labor has progressed to 5-6 cm dilation Incomplete or Inevitable Abortion 10-20 mUnit/min IV; not to exceed 30 units/12 hr

Child Dose

Renal Dose

Administration

Contra Indications

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.

Precautions

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. Lactation: May be distributed milk; commencement of nursing should be delayed for at least 1 day when discontinued; use caution

Pregnancy-Lactation

Pregnancy Category: X Lactation: May be distributed milk; commencement of nursing should be delayed for at least 1 day when discontinued; use caution

Interactions

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.

Adverse Effects

Side effects of Oxytocin : 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

Mechanism of Action

Uterine stimulant, vasopressive, & antidiuretic effects; activates G-protein-coupled receptors that trigger increases in intracellular calcium levels in uterine myofibrils, which results in uterine contractions; increases local prostaglandin production, which further stimulates uterine contraction.