1) paediatric prescribing Flashcards
What are the key differences in pharmacokinetics between adults and children?
Differences in Absorption, Distribution, Metabolism, and Excretion (ADME).
What is a neonate?
A newborn infant aged 0-28 days.
What is the age range for children in clinical pharmacology?
From 1 month to 17 years.
Why are children not just ‘mini-adults’ in terms of pharmacology?
They have different body composition, enzyme activity, organ maturity, and metabolic rates.
How does gastric pH in children affect drug absorption?
Higher gastric pH in neonates alters the solubility and absorption of weak acids (e.g., penicillins) and weak bases (e.g., itraconazole).
How does intestinal transit time in children affect drug absorption?
Slower transit time can reduce the Cmax and AUC of poorly soluble drugs like theophylline.
Why is rectal drug administration sometimes preferred in children?
It is useful when oral administration is not possible, but infants have frequent rectal contractions which may affect absorption.
How does percutaneous absorption differ in children?
Increased due to immature epidermal barrier, higher hydration, and greater surface area to body weight ratio.
Why is intramuscular drug administration usually avoided in children?
Painful and muscles are poorly perfused, leading to variable absorption.
Why is Vitamin K given intramuscularly to newborns?
To prevent haemorrhagic disease of the newborn.
How does body composition affect drug distribution in children?
Higher total body water (75-85% in neonates) increases distribution of water-soluble drugs; lower fat content affects lipophilic drug distribution.
Why is protein binding lower in neonates?
Lower serum albumin and total protein concentrations lead to increased free drug fractions of protein-bound drugs like phenytoin.
What is ‘Grey Baby Syndrome’?
A condition caused by chloramphenicol toxicity due to immature glucuronidation in neonates.
How does renal excretion develop in infants?
Glomerular filtration improves in the first week, while tubular functions mature over several months.
How does renal clearance differ in infants compared to adults?
Increased relative kidney size leads to increased renal clearance of drugs like levetiracetam and cimetidine in preschool children.
Why are children more sensitive to metoclopramide?
They are more prone to extrapyramidal side effects due to differences in drug receptor sensitivity.
How does obesity affect paediatric drug dosing?
Dosing based on total body weight may cause overdose; alternative strategies such as lean body weight-based dosing may be needed.
Why is paediatric prescribing challenging?
Limited clinical trial data, high rates of unlicensed/off-label use, and unique physiological considerations.
What percentage of paediatric prescriptions involve unlicensed or off-label use?
Between 40-90% of prescriptions.
What is an unlicensed medicine?
A drug that has never received a Marketing Authorisation for human use.
What is an off-label medicine?
A licensed drug used outside the conditions of its marketing authorisation.
Why are excipients a concern in paediatrics?
Limited safety data exist, and some excipients can be toxic at neonatal exposure levels (e.g., ethanol, propylene glycol, parabens).
How much blood alcohol concentration should not be exceeded in children under 6 years?
1 mg/100 mL (6 mg/kg).
How common are paediatric medication errors?
Affect around 13% of prescriptions and can have serious consequences.
