User Tools

Site Tools


oxytocin

oxytocin

see also:

  • Oxytocin 10 units is the preferred uterotonic agent for active management of the third stage. It is preferred over other uterotonic drugs as it is effective straight away if administered IV, and within 2 to 4 minutes of administration if given IM. It has minimal side effects and can be used in almost all women (except where there is a history of allergy to oxytocin or carbetocin).
  • Do not give ergometrine or combined oxytocin/ergometrine (Syntometrine®) to women with pre-eclampsia, eclampsia or high blood pressure because it increases the risk of convulsions and cerebrovascular accidents.

Introduction

  • oxytocin is a nine amino acid peptide natural hormone secreted by the posterior pituitary gland via positive feedback mechanisms such as touch, nipple stimulation and in labour
  • it is made in magnocellular neurosecretory cells of the supraoptic and paraventricular nuclei of the hypothalamus and is stored in Herring bodies at the axon terminals in the posterior pituitary.
  • it is also produced by some neurons in the paraventricular nucleus that project to other parts of the brain and to the spinal cord
  • oxytocin-containing cells have also been identified in several diverse tissues outside of the CNS
  • it was discovered in 1906, and in 1953, was the first ever polypeptide hormone to be sequenced and synthesized
  • it is the preferred uterotonic agent for use to augment labour and for activeED Mx of 3rd stage of labour
  • virtually all vertebrates have an oxytocin-like nonapeptide hormone that supports reproductive functions and a vasopressin-like nonapeptide hormone involved in water regulation. These genes appear to have arisen from a duplication event with the ancestral gene being some 500 million years old

Dosage

  • 3rd stage of labour: 10 units IM or IV

Mechanism of action

  • acts upon oxytocin receptors on cells (and on vasopressin V1a receptors)
  • oestrogen increases the secretion of oxytocin and to increase the expression of its receptor, the oxytocin receptor, in the brain
  • testosterone may suppress oxytocin secretion to allow hunting and aggressive behaviours
  • uterotonic
  • may reduce fetal brain activity during labour and perhaps reduce hypoxic damage
  • let down of milk in lactation in response to nipple stimulation by the baby
  • regression of the corpus luteum
  • pair bonding, attachment, altruism and social relationships
  • may play a role in recognition, sexual arousal, erections, orgasms, trust, reducing anxiety, reducing stress, enabling sleep, and in reducing cravings in addiction1)
  • role in triggering group defensive behaviours
  • role in formation of emotional memories
  • role in sperm movement, contracting ejaculatory tissues (via vasopressin V1a receptors), and production of testosterone in men
  • may also have roles in bone formation, glycaemia, male sexuality, cardiac differentiation, and nonregulated cellular proliferation
  • may reduce inflammation and increase wound healing
  • high levels may have a role in development of benign prostatic hyperplasia (BPH)
  • low levels may have a role in depression

Contraindications

  • pregnancy except in labour and in ED Mx of 3rd stage of labour
  • hypersensitivity to oxytocin
  • during labour if patient should be considered for a LUSCS instead
    • cephalopelvic disproportion
    • fetal distress
    • PH LUSCS
    • etc.

Adverse effects

  • painful uterine contractions
  • when given in labour, it may cause:
    • fetal distress
    • uterine rupture (rare)
    • retinal haemorrhage in newborns
    • increased neonatal jaundice
  • high doses can cause:
  • most other adverse effects are minor or rare
oxytocin.txt · Last modified: 2020/06/01 21:09 by gary1