Intrapartum Care: Drugs in Labour Flashcards
What is oxytocin?
A hormone secreted by the posterior pituitary gland but produced in the hypothalamus.
What role does oxytocin play in labour (3 things)?
1) stimulates the ripening of the cervix
2) stimulates contractions of uterus during labour and delivery
3) role in lactation during breastfeeding
What are oxytocin infusions used for in labour?
1) induce labour
2) progress labour
3) improve the frequency and strength of uterine contractions
4) prevent or treat postpartum haemorrhage
What is Syntocinon?
Syntocinon is a brand name for oxytocin produced by one drug company.
What class of drug is Atosiban?
An oxytocin receptor antagonist.
What can be used as an alternative to nifedipine for tocolysis in premature labour (when nifedipine is contraindicated)?
Atosiban
What is ergometrine?
It is derived from ergot plants.
Role of ergometrine in labour?
It stimulates smooth muscle contraction, both in the uterus and blood vessels so:
1) useful for delivery of placenta (3rd stage of labour)
2) reduce postpartum bleeding
When is ergometrine ONLY used?
After the delivery of the baby (not in the 1st or 2nd stage of labour)
Side effects of ergometrine?
Due to action on smooth muscles in blood vessels and GI tract:
1) HTN
2) Diarrhoea
3) Vomiting
4) Angina: causes coronary artery spasm
Who should ergometrine be avoided in?
1) Pre-eclampsia
2) HTN: use with significant caution
What is Syntometrine?
Syntometrine is a combination drug containing oxytocin (Syntocinon) and ergometrine.
Indication of Syntometrine in labour?
It can be used for prevention or treatment of postpartum haemorrhage.
Often used as an alternative to oxytocin in the active management of third stage of labour.
Indications for syntocinon in labour?
1) stimulates the contraction of the uterus
2) reduces risk of postpartum haemorrhage
3) induce labour
Mechanism of Ergometrine?
stimulates alpha-adrenergic, dopaminergic and serotonergic receptors
Role of prostaglandins in labour?
1) Stimulate contraction of uterine muscles
2) Have a role in ripening the cervix before delivery
What is one key prostaglandin to be aware of in labour?
Dinoprostone (prostaglandin E2)
Indication for dinoprostone?
Induction of labour
What 3 forms can dinoprostone come in?
1) vaginal pessaries (Propess)
2) vaginal tablets (Prostin tablets)
3) Vaginal gel (Prostin gel)
What class of drugs inhibit prostaglandins?
NSAIDs e.g. ibuprofen, naproxen
Impact of prostaglandins on BP?
Act as vasodilators and lower BP
How do NSAIDs affect BP?
Cause raised BP due to inhibiting prostaglandins
Why are NSAIDs generally avoided in pregnancy?
Can raise BP
Why are NSAIDs particuarly useful for dysmenorrhoea (painful periods)?
Block prostaglandins - reduce painful cramping of the uterus during menstruation.
What is misoprostol?
Misoprostol is a prostaglandin analogue: i.e. binds to prostaglandin receptors and activates them
Indication of misoprostol in labour?
1) It is used as medical management in miscarriage, to help complete the miscarriage.
2) Used alongside mifepristone for abortions
3) Induction of labour after intrauterine fetal death
What is mifepristone?
An anti-progestogen medication that blocks the action of progesterone, halting the pregnancy and ripening the cervix.
Indication of Mifepristone in pregnancy?
1) abortions (used alongside misoprostol for abortions)
2) induction of labour of labour after intrauterine fetal death
Mechanism of mifepristone?
1) anti-progestogen
2) halts the pregnancy and ripening the cervix
3) enhances effects of prostaglandins to stimulate contraction of uterus
When is mifepristone NOT used?
It is not used during pregnancy with a healthy living fetus.
What class of drug nifedipine?
Calcium channel blocker
Mechanism of nifedipine?
Calcium channel bloker that acts to reduce smooth muscle contraction in blood vessels and uterus.
2 main indications of nifedipine?
1) HTN and pre-eclampsia: reduce BP
2) Premature labour: tocolysis, where it suppresses uterine activity and delays the onset of labour
What class of drug is terbutaline?
Beta-2 agonist (similar to salbutamol)
Mechanism of terbutaline?
Stimulates beta-2 adrenergic receptors. It acts on the smooth muscle of the uterus to suppress uterine contractions.
Indication for terbutaline?
Tocolysis in uterine hyperstimulation, notably when the uterine contractions become excessive during induction of labour.
What class of drug is carboprost?
A synthetic prostaglandin analogue (i.e. binds to prostaglandin receptors)
Mechanism of carboprost?
Binds to prostaglandin receptors and stimulates uterine contraction.
Indication of carboprost?
Given as deep IM injection in postpartum haemorrhage where ergometrine and oxytocin have been inadequate
Contraindication of carboprost?
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.
How is carboprost given?
Deep IM injection
What is tranexamic acid?
An antifibrinoyltic medication that reduces bleeding
Mechanism of tranexamic acid
1) Binds to plasminogen and prevents it from converting to plasmin.
2) Plasmin is an enzyme that works to dissolve the fibrin within blood clots.
3) Therefore, by decreasing the activity of the enzyme plasmin, tranexamic acid helps prevent the breakdown of blood clots.
What is fibrin?
Fibrin is a protein that helps hold blood clots together.
Indication of tranexamic acid?
Tranexamic acid is used in the prevention and treatment of postpartum haemorrhage.
What is failure to progress?
Failure to progress refers to when labour is not developing at a satisfactory rate.
This increases the risk to the fetus and the mother.