Oxytocin information from DrugsUpdate
L - Caution when used during lactation
Oxytocin (sold as Pitocin, Syntocinon) is a mammalian hormone that also acts as a neurotransmitter in the brain.
It is best known for its roles in female reproduction: it is released in large amounts after distension of the cervix and vagina during labor, and after stimulation of the nipples, facilitating birth and breastfeeding, respectively. Recent studies have begun to investigate oxytocin's role in various behaviors, including orgasm, social recognition, pair bonding, anxiety, trust, love, and maternal behaviors.
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.
Uterine contractions: IM: 3-5 minutes; IV: approx 1 minute.
IM: 2-3 hours; IV: 1 hour.
Steady state is reached normally 40 minutes after parenteral admin.
Distribution throughout extracellular fluid, small amounts reach foetus.
Rapidly via the liver and plasma (by oxytocinase); some metabolism via mammary gland.
Elimination half-life: 1-5 minutes; excreted via urine.
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 hours); prolonged uterine contractions causing foetal hypoxia and death; rupture of gravid uterus; afibrinogenaemia; subarachnoid haemorrhage
Oxytocin is not indicated for elective induction of labor.
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.
CV disorders; >35 years; 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.
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.
Adjunct in abortion
Adult: 10-20 milliunits/minute. Max total dose: 30 units in a 12-hours period.
Adult: 10-40 units by infusion in 1000 mL of IV fluid at a rate sufficient to control uterine atony.
Adult: 1-2 milliunits/minute, may increase at intervals of at least 30 minutes until a max of 3-4 contractions occur every 10 minutes. Not to exceed 32 milliunits/minute and no more than a total of 5 units should be given in 1 day. Not to be given within 6 hours after admin of vaginal prostaglandins. Monitor uterine contractions and foetal heart rate continuously. Withdraw gradually once labour is progressing.
Oxytocin challenge test for evaluating of foetal distress
Adult: Dilute 5–10 units in 1 L of 5% dextrose injection. Initially, administer the drug in the mother via IV infusion at a rate of 0.5 milliunits/minute. May gradually increase infusion rate at intervals of 15-30 minutes. Max: 20 milliunits/minute. Monitor foetal heart rate and uterine contractions immediately before and during infusion. Discontinue infusion when 3 moderate uterine contractions occur within one 10-minute interval. Compare baseline and oxytocin-induced foetal heart rates. If no change occurs, repeat the test in 1 week. Termination of pregnancy may be required if a late deceleration in foetal heart rate occurs.
Adult: 1 spray (4 units) into 1 nostril 5 minutes before suckling.
Postpartum uterine bleeding: oxytocin 10-40 units to running IV infusion, max 40 units/1000 ml.
When admixed: fibrinolysin (human), norepinephrine, prochlorperazine edisylate, warfarin; variable compatibility with phytonadione.
List of Contraindications
Contraindicated in pregnancy
Category X: Studies in animals or human beings have demonstrated foetal abnormalities or there is evidence of foetal risk based on human experience or both, and the risk of the use of the drug in pregnant women clearly outweighs any possible benefit. The drug is contraindicated in women who are or may become pregnant.
Caution when used during lactation
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.
Store at 2-8 °C.
Store at 2-8 °C.