Pharmacology In pregnancy and breast feeding

Question 1

What is pharmacokinetics?

Answer 1

It is the effect that the body has on drugs

Question 2

What is pharmacodynamics?

Answer 2

Its the effect that the drug has on the body

Question 3

How many % of women take a PRESCRIBED medicine during pregnancy?

Answer 3

60%

Question 4

How many % of women take OTC medicine during pregnancy?

Answer 4

90%

Question 5

How many women of child-bearing age take medication?

Answer 5

80%

Question 6

What absorption changes occur in pregnancy?

Answer 6

Morning sickness might limit oral intake
Gastric emptying and gut motility decreases

Blood flow increases so subcutaneous and intramuscular routes might be absorbed quicker

Inhalation increases which can ^ inhaled drug absorption

Question 7

When does morning sickness most occur in pregnancy?

Answer 7

First 3 months.

Question 8

What happens to the fraction of free drugs in pregnancy?

Answer 8

They increase (because plasma is diluted and theres not as many plasma proteins)

Question 9

What happens to the volume of distribution in pregnancy?

Answer 9

This increases due to the plasma volume and fat increasing.

Question 10

What happens to the metabolism of drugs in pregnancy?

Answer 10

oestrogen and progesterone can induce or inhibit liver P450 enzymes - increasing or decreasing metabolism.

Question 11

What happens to excretion in pregnancy?

Answer 11

it increases, GFR increases by 50%.

Doses might need to be increased progressively as the pregnancy progresses.

Question 12

Which drugs can cross the placenta?

Answer 12

Most drugs can cross the placenta. You should assume that all drugs can.

Question 13

What makes a drug more likely to cross the placenta?

Answer 13

molecular weight - smaller sizes will cross more easily

polarity - unionised crosses more easily

lipid solubility - lipid soluble drugs will cross more readily

Question 14

Why is the drugs different in the foetus?

Answer 14

• circulation is different
• less protein - more free drugs
• more blood flow to brain, less developed blood brain barrier

Question 15

How do the foetus metabolise the drug?

Answer 15

slower, theres less P450 enzymes but they increase with gestation.

Question 16

How does the foetus excrete of the drug?

Answer 16

Into the amniotic fluid, but it can be re swallowed by the foetus, they can accumulate and cause toxicity.

Question 17

What is most common in the first trimester of gestation?

Answer 17

teratogenicity

Question 18

What is most common in the second and third trimester of gestation?

Answer 18

fetotoxicity

Question 19

What are the principles of prescribing for women of the child bearing age?

Answer 19

• always consider pregnancy
• warm of possible risks
• tell a women to try and attend the doctor before they get pregnant when treating a condition
• discuss contraception if prescribing teratogenic medicines
• don’t prescribe certain drugs without contraception

Question 20

How many foetal abnormalities are drugs a cause of?

Answer 20

2% of foetal abnormalities

Question 21

When is the foetus at highest risk of teratogenicity?

Answer 21

during organogenesis (3-8 weeks)

Question 22

how do drugs block the folate metabolism?

Answer 22

• They can bind to the enzyme (tetra hydrofolate reductase) to block the conversion of folate
• they can block other enzymes

Question 23

What does folate antagonism lead to?

Answer 23

Oro-facial, neural tube or limb defects.

Question 24

What do retinoid drugs cause for the foetus?

Answer 24

• aortic arch anomalies
• ventricular septal defects
• craniofacial malformations
• oesophageal atresia
• pharyngeal gland abnormalities

Question 25

Which drugs cause enzyme-mediated teratogenesis?

Answer 25

NSAIDs - can cause orofacial clefts and cardiac septal defects

Question 26

What effect does fetotoxicity have on the foetus?

Answer 26

• growth retardation
• structural malformations
• fetal death
• functional impairment
• carcinogenesis

Question 27

Which drugs often cause fetotoxicity?

Answer 27

ACE inhibitors, ARBs.

Question 28

Which drugs are teratogenic in the foetus?

Answer 28

Anticonvulsants - sodium valproate
anticoagulants 
antihypertensives
NSAIDs
Alcohol
Retinoids

Question 29

Which antihypertensive agents aren’t teratogenic?

Answer 29

Methyl dopa, labetalol, nifedipine.

Question 30

Which drugs are present in milk?

Answer 30

Any drug the mother takes is present in the milk.

Question 31

When is the best time for a mother to take her medication?

Answer 31

As soon as she has fed her baby.

Question 32

Are protein or lipid soluble drugs preferred in breastfeeding?

Answer 32

Protein soluble.

These are less likely to bind to the lipid component of breast milk.

Question 33

Which drugs should be avoided in breast feeding?

Answer 33

immunosuppressants 
anti-convulsants
amiodarone 
lithium
radio-iodine

Question 34

What are galactagogues?

Answer 34

Medications (can be OTC) which are used to induce, maintain and increase milk production.

Question 35

What are two common galactagogues?

Answer 35

Fenugreek

Comfrey

Question 36

When is trimethoprim teratogenic?

Answer 36

Usually just in the first trimester, apart from that it’s safe. But avoid use if possible.