Paediatrics Flashcards
Distribution is affected by:
1) Absorption
2) Penetration of biological membrane
3) Perfusion of organs
4) Drugs disposition to distribute
5) Drugs affinity for protein binding
Comment on the Body Composition in Neonates
Extracellular fluid volume is higher in neonates, and total body water content is higher in neonates compared to adults
less than 3% of a neonate is fat
30 % of 1 Year olds is fat
less than 18% of adults is fat.
Comment on blood protein content pediatrics and the implications it has on drug binding. Give examples where applicable.
Less protein available for drug binding. This means that there is higher competition for binding sites. This leads to displacement of endogenous substances
e.g bilirubin.
what happens if bilirubin gets displaced? and Give examples of what displaces it
Bilirubin displacement, particularly in the brain leads to toxicity.
e.g Sulphonamides and Ceftriaxone in neonate.
In terms of oral absorption, how does oral absorption in neonates differ from adults? Comment on gastric pH,
Delayed Gastric emptying and transition time
Reduced gastric acid secretion
At birth stomach pH is 7, and this normalises after 2 yrs
what effect does reduced gastric acid secretion have on drugs in paediatrics? Give an example
Reduced absorption of drugs that require an acidic environment. E.g Metronidazole
Comment on topical absorption in neonates. Higher or lower and why?
Higher. There’s an increased rate and extent of absorption. Due to an immature epidermal barrier, Increased skin hydration and a higher SA to body weight ratio.
what can topical administration lead to in neonate? e.g?
Toxicity! e.g Chlorhexidine (burns)
Corticosteroids (cushings syndrome)
Is parenteral absorption a good idea in neonates why not?
Smaller veins so hard to administer the drug.
They have less muscle mass so IM is painful and the absorption is unpredictable.
What key enzyme develops slowly in neonates?
CYP450
how long does it take to reach phase 1 and phase 2 capacity?
- 6-12 months for phase 1
- 3 years for full capacity in phase 2.
Excretion - is this constant? What does this mean in terms of drugs
No wide inter-variation = difficult to predict drug clearance.
State the effects Ceftriaxone, and Metoclopramide has on babies
Ceftriaxone - Displaces bilirubin
Metoclopramide can cause EPSEs
What is dosing in children based on?? and how do you calculate BSA (body surface area)
Based on weight
Based on age
BSA (body surface area) = square root of Bw * Ht/ 3600
State two key excipients that have adverse effects
Benzylalcohol can cause circulatory collapse
Propylene glycol can cause seizures
