31. Pharmacology

Question 1

What should you do when prescribing for kids?

Answer 1

BNF C

don’t just ask a mate- Malay will get you

Question 2

Why are drug interactions different in kids?

Answer 2

Affected by age, size, nutrition and growth

Especially true for neonates, physiological variables change rapidly

Question 3

What are the hardest children to treat with the drugs

Answer 3

The younger the worse

Question 4

What classes of mother drugs can affect children?

Answer 4

Beta blockers- seizures

Opioids- dependence

Breast milk can transfer drugs from mother to child

Question 5

What are the principles in prescribing for children?

Answer 5

Use the simplest dose

Pay attention to route, formulation and duration of therapy

Always check BNFc

Question 6

What is phacomelia?

Answer 6

A lack of limb development due to thalidomide toxicity in children

Question 7

What are the new criteria set after the thalidomide crisis?

Answer 7

A drug must be licensed before marketing

Drugs must be shown to be safe, effective and of a high quality

The EMA or CHM (UK) license drugs and can withdraw drugs

Question 8

What is the difference between adult and chid drug prescribing?

Answer 8

Major pharmacokinetic differences

Altered pharmacodynamic response

Effects on growth and development not known

Different specific pathologies

Question 9

What can be said about medicines used in children?

Answer 9

70% of medicines have never been studied in children

Many medicines are used off label (unlicensed)

Question 10

What are unlicensed medicines?

Answer 10

Don’t have license in Europe or Britain for human use

Also includes when you change the medium or a drug e.g. crushing up digoxin in syrup

Question 11

Give some examples of off label prescribing

Answer 11

Changing medium

Medicines used for an indication not intended

Medicines used at a different dose

Medicines only being used in clinical trials

Question 12

How common is off label prescribing?

Answer 12

Neonates 60-90%

Children 10-15% in hospital,
30% in the community

Question 13

What is the problem of using off label drugs?

Answer 13

No evidence of efficacy, ADR’s and toxicity

Question 14

What happens to drug clearance in children?

Answer 14

Clearance increases till puberty

At puberty it drops by around 15%. This leads to increased toxicity during puberty

Question 15

What are the problems with paroxetine?

Answer 15

SSRI, when used in children there is a 4 fold increase in suicide

Question 16

What is the problem with oral administration of medication?

Answer 16

Delayed gastric emptying

Absorption reaches adult values by 6-8 months old

Bioavailability of drugs with high hepatic clearance and first pass elimination is reduced and highly variable

Drugs which rely on entero-hepatic are variable

Question 17

What are the differences of skin absorption in children?

Answer 17

Enhanced in infants and children, especially with damaged skin

Question 18

What are the differences of rectal absorption in children?

Answer 18

Used in patients who are vomiting or who are unwilling to take oral medication.

Avoids first-pass metabolism.

Not ideal as significant variation, few preparations, trauma.

Question 19

How is renal excretion changed in children?

Answer 19

Renal excretion is decreased in neonates and
shows progressive maturation with age.

Adult values are achieved at 3-6 months and
tubular function at 12 months.

Consideration of renal function is most
important in the neonate

Question 20

How does the liver affect metabolism?

Answer 20

Neonates are especially sensitive to drugs eliminated by hepatic metabolism

Metabolic activity increases rapidly from about 1 month after birth with adult activity by 1 year of age

Question 21

Summarise the big differences between neonates and children?

Answer 21

Decreased albumin- increased free drug levels

Increased free drug levels- increased drug response

Decreased hepatic metabolism- increased drug response

Decreased renal elimination- increased drug response

Decreased blood brain barrier- increased CNS effects