Paediatric and older age Prescribing

Question 1

How is absorption different in babies?

Answer 1

• increased absorption of topical agents as SA:body weight greater
• Intramuscular reduced due to reduced mass
• rectal absorption efficient

Question 2

How is distribution different in babies?

Answer 2

• higher body water % so loading dose is greater

- albumin binding lower increasing free conc of bound drugs

Question 3

How is metabolism different in babies?

Answer 3

• impaired oxidation increasing drug conc

- impaired glucuronidation increasing risk of toxicity

Question 4

How is elimination different in babies?

Answer 4

• glomerular filtration secretion and reabsorption impaired, need lower dose for renal cleared drugs
• by 6month renal function normal so body weight can be used to dose

Question 5

What inherited conditions can affect drug response in babies?

Answer 5

• oxidation/acetylation (fast or slow)
• Glucose-6-phosphate dehydrogenase deficiency
• pseudocholinesterase (prolonged apnoea)

Question 6

How does prescribing change in the elderly?

Answer 6

• more likely to have more diseases so taking many drugs
• adherence reduced in frail elderly
• drug disposition and responsiveness tend to change resulting in dose modification

Question 7

How does the pharmacokinetics change for elderly patients?

Answer 7

1) absorption delayed
2) Distribution (body mass and total body water decrease increasing plasma conc of drugs
3) metabolism slower due to reduced liver mass and BF so drugs undergoing metabolism act longer
4) elimination by kidney reduced and toxicity more likely

Question 8

What should be considered about BP medication in the elderly?

Answer 8

• baroreceptor function impaired increasing risk of postural hypotension
• response to beta blockers impaired and so other antihypertensives better

Question 9

What drugs should be stopped in patients with AKI

Answer 9

D - diuretics
A - ace-i
M - metformin
N - NSAIDs