Obstetric pharmacology

Question 1

What is the global leading cause of maternal death?
What are other common causes?
What the main cause in developing countries (Africa)?

Answer 1

Cardiovascular disease
Haemorrphage, pre-eclampsia & thromboembolis also common

Haemorrphage leading cause in Africa

Question 2

What are important drugs for treating obstetric haemorrhage?
How do they work?
Limitations?

Answer 2

Oxytocin - contraction of smooth muscle cells
Hypotension, tachycardia

Ergometrine - contraction of SMCs + smooth muscle of vessels
C/I in pre-eclampsia as it can cause hypertension
Can also cause N/V

Misoprostol (prostaglandin) - contraction of smooth muscle cells

Question 3

What are some antibiotics important in STIs/Congenital infections & maternal sepsis?

Answer 3

3rd generation cephalsporins
Macrolides (azthromycin)
Gentamicin 
Ampicilin 
Metranidazole

Question 4

What are important drugs for treating pre-eclampsia?
How do they work?
Limitations?

Answer 4

Magnesium sulfates - reduces intracellular calcium, weak calcium channel antagonist
Prevention or treatment of seizures

Have calcium gluconate on hand in case get magnesium toxicity - respiratory & cardiac depression

Labetalol - beta-blocker (competitive non-selective beta & selective alpha-1)

Question 5

Is important in metabolising drugs in pregnancy?

What drug properties influence its ability to cross the placenta?

Answer 5

The placenta

Molecular size, lipid solubility and degree of ionisation

Question 6

What are important pharmacological principles for lactating woman?

Answer 6

Minimise drug in breast milk
Minimise disruption to breast feeding
Effectively treat maternal condition

Question 7

What features of drugs influence teratogenic effect?

Answer 7

The dose
That is a known teratogen in humans
The timing of dose in gestation (generally more teratogenic in embryonic period 3 - 8 weeks)

Question 8

What are examples of human teratogens?

Answer 8

Environmental & physical agents - i.e. radiation
Infection - i.e. rubella
Chemicals/drugs - i.e. thalidomide, vitamin A, ACEI, warfarin, tetracyclines
Maternal metabolic imbalance - diabetes, folic acid deficiency

Question 9

What is considered a major obstetric haemorrhage?

Answer 9

> 1500 mL blood loss post partum

Question 10

Drugs important in pre-term labour?

Answer 10

Nifdepine - calcium channel blocker - inhibits uterine contraction
Dexamethosone - maturation of foetal lungs

Question 11

In developing countries what infection commonly causes maternal & neonatal death due to unclean deliveries and umbilical cord practises?

Answer 11

Tetanus

Question 12

What is pre-clampsia?

What are the complications?

Answer 12

Complicated hypertension
Beings around 20+ weeks gestation and resolves ~3/12 postpartum

Same as normal hypertension
CVD
Cerebrovascular disease
CKD
Heart failure
Peripheral vascular disease

Question 13

What is the general management of pre-ecampsia

Answer 13

Early involvement of senior physician & inter-discipilary team
Treatment with anti-hypertensives + MgSO4 for prevention of seizures
Don’t use ergometrine as it has side effect of hypertension
Careful fluid balance as there is risk of pulmonary oedema