Obstetrics

Question 1

Syntocin/ Oxytocin

what is it
from where

Where does it act

Answer 1

Oxytocin is a naturally occurring peptide,

secreted from post pituitary;

syntocinon is a synthetic analogue.

They are agonists for oxytocin receptors on myometrial cells and stimulate uterine contraction.

Question 2

Syntocin uses

Answer 2

Initiation, maintenance and augmentation of labour and used routinely at caesarean section delivery

Oxytocin is also used for the control of postpartum haemorrhage due to uterine hypotonia.
It is given by intravenous infusion or a “slow” bolus, the latter a dose of 5 IU. A dose of 10 IU increases the risk of cardiovascular complications.

Question 3

Oxytocin
inactivated where by what
t1/2

Answer 3

Oxytocin is inactivated in the liver and kidneys and by circulating oxytocinase.
The T1/2 is approximately 5-minutes.

Question 4

Complications of oxytocin

Answer 4

Complications include:

1 Transient fall in systemic vascular resistance, blood pressure and a reflex tachycardia.

2 Increase in stroke volume and therefore cardiac output

3 Skin flushing from cutaneous vasodilatation

4 Autotransfusion from uterine contraction

5 Reduced uteroplacental blood flow, and

6 Water intoxication in mother and foetus if large doses are used.