Therapeutics- Prescribing in Special Groups- Pregnant Women

Question 1

In general should medications for chronic disorders be stopped during pregnancy?

Answer 1

No it is usually better not to stop

Risk from untreated disease is usually greater as it can adversely effect the pregnancy

Question 2

Are OTC drugs safe to use in pregnancy?

Answer 2

Yes, generally any adverse effects would cause the drug to not be available OTS

Question 3

How does ECF change during pregnancy?

Answer 3

ECF increases and therefore the renal clearance of renally cleared drugs increases

Question 4

How does drug absorption change?

Answer 4

Nausea and vomiting can occur during pregnancy which can reduce absorption of oral drugs. GI transit time also increases which delays absorption

Question 5

How does absorption from IM injections change?

Answer 5

Blood flow increases and so absorption increases

Question 6

How does absorption from inhaled medications change?

Answer 6

Blood flow increases (ECF increases) and so absorption increases

Question 7

When are foetuses most sensitive to teratogens?

Answer 7

During the first trimester as this is when the development of major organs is occuring

Question 8

What is a teratogen?

Answer 8

A substance, organism, physical agent or deficiency state capable of inducing abnormal structure or function

Question 9

What percentage of prescribed drugs are known teratogens?

Answer 9

1%

Question 10

How many congenital malformations are due to drugs?

Answer 10

2-3%

Question 11

What is the all or nothing effect during the pre-embryonic phase?

Answer 11

This is in the first 14 days

Insult at this stage either leads to spontaneous recovery or loss

Question 12

What effect could teratogenic drugs have during the first or second trimester?

Answer 12

Affect growth
Affect functional development
Toxic effect on tissues- Fetotoxicity

Question 13

What are some drugs to be avoided in pregnancy?

Answer 13

ACEi
ARBs
Quinolone antibiotics
Tetracyclines
Warfarin
Sodium Valproate
Androgens
Opiates

Question 14

What changes occur to maternal drug concentration in pregnancy?

Answer 14

As ECF increases and renal clearance decreases the concentration will be reduced compared to a non-pregnant woman with the same dose
Foetal and placental metabolism also affect drug concentrations

Question 15

Till what age is it advised to exclusively breast feed?

Answer 15

6 months

Question 16

Why are neonates most at risks with drugs that can be excreted in the breast milk?

Answer 16

They have immature excretory functions and so there is a risk of drug accumulation

Question 17

What characteristics would make a drug less likely to enter the breast milk?

Answer 17

High molecular weight
Low lipid solubility
High protein binding in the plasma
Lower pH- breast milk has a lower pH than plasma and so acidic drugs (e.g. amoxicillin) will be less likely to enter the breast milk

Question 18

Which drugs should be avoided in breastfeeding?

Answer 18

Amiodarone
Antithyroid drugs- can cause neonatal goitre and hypo-thyroidism
Benzodiazepines- enter the breast milk
Lithium salts- Present in breast milk and risk of toxicity
Radioactive iodine
Statins- high concentration in breast milk
Sulphonamides

Question 19

How might certain drugs affect lactation?

Answer 19

Dopamine prevents prolactin release and so dopamine agonists can reduce prolactin release
This decreases milk production

Question 20

Give an example of a dopamine agonist/antagonst

Answer 20

Agonist- cabergoline

Antagonist- Domperidone

Question 21

What are the age categorisations?

Answer 21

Premature baby- less than 36 weeks
Newborm/Neonate- Up to 27 days old
Infant- 28 days to 23 months old
Child- 2 years to 11 years
Adolescent- 12 years to 16 years

Question 22

How is oral absorption different in children?

Answer 22

Absorption is affected by slower gastric emptying which takes 6-8 months to reach adult levels

Question 23

How is the uptake of IM drugs altered in children?

Answer 23

Neonates have a low muscle mass and there is variability in blood flow to muscles making IM absorption unpredictable

Question 24

How is percutaneous drug absorption different in children?

Answer 24

Percutaneous absorption is increased as the stratum corneum is thinner in children and there is increased skin hydration

Question 25

How is the distribution of water soluble drugs different in children?

Answer 25

Children have a much higher % of body water and so there is a greater volume of distribution for water soluble drugs. This decreases as children age. This causes lower concentration of the drug so higher doses may be required (e.g. Gentamicin)

Question 26

How is the binding of drugs to plasma proteins altered in children?

Answer 26

Neonates have less plasma proteins and so binding is reduced. This can cause increases in the free and active form of the drug

Question 27

Why might sulphonamides cause jaundice?

Answer 27

They can displace bilirubin from albumin and this increase in bilirubin causes jaundice

Question 28

How is excretion different in neonates compared to adults?

Answer 28

Neonates have reduced ability to excrete drugs. Renal function is not fully developed and so the elimination of renally cleared drugs is reduced, drugs cleared by the kidney’s can therefore accumulate (e.g. gentamicin)

Question 29

What measurements may be used when deciding doses for children?

Answer 29

Age banding- low therapeutic index drugs (parcetemol, amoxicillin)
Weight- many drugs
Surface Area- for small therapeutic index drugs

Question 30

Over what age are children classed as adults for dosing purposes?

Answer 30

12 years

Question 31

What colour should syringes be for orally given drugs?

Answer 31

Purple

These syringes are not compatible with IV lines, this prevents incorrect administration of the drug

Question 32

What is the intraosseous route? When might it be used?

Answer 32

This is delivery of drugs into the bone marrow
It is used in paediatric emergency situations
The bone marrow is highly vascular

Question 33

Which drugs should be avoided in children?

Answer 33

Tetracyclines- Cause yellow discolouration of teeth (Not given to children under 12)
Aspirin- Risk of Reye’s Sndrome (Should not be given to children under 16)
Cloramphenicol- Grey Baby Syndrome in neonates