Drugs in Labour

Question 1

What is the role of oxytocin?

Answer 1

Oxytocin is a hormone secreted by the posterior pituitary gland. It is produced in the hypothalamus, but travels to the pituitary before being released into the general circulation. It has several effects on mood and social interactions in everyday life, but also plays a vital role in labour and delivery.

Oxytocin stimulates the ripening of the cervix and contractions of the uterus during labour and delivery. It also plays a role in lactation during breastfeeding.

Question 2

What are the indications of oxytocin?

Answer 2

Infusions of oxytocin are used to:

• Induce labour
• Progress labour
• Improve the frequency and strength of uterine contractions
• Prevent or treat postpartum haemorrhage

Question 3

What is the role of atosiban?

Answer 3

Atosiban is an oxytocin receptor antagonist that can be used as an alternative to nifedipine for tocolysis in premature labour (when nifedipine is contraindicated).

Question 4

What is the role of ergometrine?

Answer 4

Ergometrine is derived from ergot plants. It stimulates smooth muscle contraction, both in the uterus and blood vessels. This makes it useful for delivery of the placenta and to reduce postpartum bleeding.

Question 5

What are the indications of ergometrine?

Answer 5

It may be used during the third stage of labour (delivery of the placenta) and postpartum to prevent and treat postpartum haemorrhage. It is only used after delivery of the baby, not in the first or second stage.

Question 6

What are the side effects of ergometrine?

Answer 6

Due to the action on the smooth muscle in blood vessels and gastrointestinal tract, it can cause several side effects, including hypertension, diarrhoea, vomiting and angina.

Question 7

When should ergometrine be avoided?

Answer 7

It needs to be avoided in eclampsia, and used only with significant caution in patients with hypertension.

Question 8

What is the role of syntometrine?

Answer 8

Syntometrine is a combination drug containing oxytocin (Syntocinon) and ergometrine. It can be used for prevention or treatment of postpartum haemorrhage.

Question 9

What is the role of prostaglandins?

Answer 9

Prostaglandins act like local hormones, triggering specific effects in local tissues. Tissues throughout the entire body contain and respond to prostaglandins. They play a crucial role in menstruation and labour by stimulating contraction of the uterine muscles. They also have a role in ripening the cervix before delivery.

Question 10

Give an example of a prostaglandin

Answer 10

One key prostaglandin to be aware of is dinoprostone, which is prostaglandin E2.

Question 11

What are the indications of prostoglandins?

Answer 11

This is used for induction of labour.

Question 12

What are the 3 forms of prostoglandins?

Answer 12

• Vaginal pessaries (Propess)
• Vaginal tablets (Prostin tablets)
• Vaginal gel (Prostin gel)

Question 13

What effect do prostaglandins have on blood pressure?

Answer 13

Prostaglandins act as vasodilators, and lower blood pressure.

Question 14

What is the role of misoprostol?

Answer 14

Misoprostol is a prostaglandin analogue, meaning it binds to prostaglandin receptors and activates them. It is used as medical management in miscarriage, to help complete the miscarriage. Misoprostol is used alongside mifepristone for abortions, and induction of labour after intrauterine fetal death.

Question 15

What is the role of mifepristone?

Answer 15

Mifepristone is an anti-progestogen medication that blocks the action of progesterone, halting the pregnancy and ripening the cervix. It enhances the effects of prostaglandins to stimulate contraction of the uterus. Mifepristone is used alongside misoprostol for abortions, and induction of labour after intrauterine fetal death. It is not used during pregnancy with a healthy living fetus.

Question 16

What is the role of nifedipine?

Answer 16

Nifedipine is a calcium channel blocker that acts to reduce smooth muscle contraction in blood vessels and the uterus. It has two main uses in pregnancy:

• Reduce blood pressure in hypertension and pre-eclampsia
• Tocolysis in premature labour, where it suppresses uterine activity and delays the onset of labour

Question 17

What is the role of terbutaline?

Answer 17

Terbutaline is a beta-2 agonist, similar to salbutamol. It stimulates beta-2 adrenergic receptors. It acts on the smooth muscle of the uterus to suppress uterine contractions. It is used for tocolysis in uterine hyperstimulation, notably when the uterine contractions become excessive during induction of labour.

Question 18

What is the role of carboprost?

Answer 18

Carboprost is a synthetic prostaglandin analogue, meaning it binds to prostaglandin receptors. It stimulates uterine contraction. It is given as a deep intramuscular injection in postpartum haemorrhage, where ergometrine and oxytocin have been inadequate. Notably, it needs to be avoided or used with particular caution in patients with asthma, as it can cause a potentially life-threatening exacerbation of the asthma.

Question 19

What is the role of tranexamic acid?

Answer 19

Tranexamic acid is an antifibrinolytic medication that reduces bleeding. It binds to plasminogen and prevents it from converting to plasmin. Plasmin is an enzyme that works to dissolve the fibrin within blood clots. Fibrin is a protein that helps hold blood clots together. Therefore, by decreasing the activity of the enzyme plasmin, tranexamic acid helps prevent the breakdown of blood clots.

Tranexamic acid is used in the prevention and treatment of postpartum haemorrhage.