Paediatric pharmacology Flashcards
What is the difference between the following?
- Premature baby
- Full term baby
- Neonate
- Infant
- Child
- Young adult
- Premature = born before 37 weeks
- Full term baby = born 37-42 weeks gestation
- Neonate = baby up to 4 weeks old
- Infant = baby up to 1 year old
- Child = 1-12 years old
- Young adult = teens upwards
Pharmacokinetics vs pharmacodynamics?
Pharmacokinetics = ADME (body effect on drug)
Pharmacodynamics = drug effect on body
What are factors which affect drug dose and response?
- Growth + development of organs
- Drug absorption - eg. oral, IM, SC
- Drug distribution
- Metabolism
- Excretion
What is the most common route for absorption?
Oral -> Gastrointestinal
How is gastrointestinal absorption different for neonates?
- Newborns have reduced gastric acid secretion (normalise at 3yo)
- Gastric emptying slower in neonates
- Intestinal motility + integrity affect extent of drug absorption
- Disorders of GI tract affect absorption of orally administered drugs eg. gastroschisis
Oral route is unpredictable!
For intramuscular absorption, the absorption from injection site can be erratic. It depends on what factors?
- Vascular perfusion
- Muscular contraction
- Muscle mass
- Avascular tissue
- Shock
Are intramuscular injections encouraged in children?
- In ill neonates muscle blood flow varies considerably - sepsis, hypotension
- Not suitable for large number of drugs
- In general IM injections are discouraged in children - can be distressing + painful
Why is there an enhanced effect of percutaneous absorbed drugs in neonates?
- They have decreased thickness of stratum corneum
- Increased skin hydration
- Increased SA
What impact do topically applied corticosteroids have on children?
Lead to significant systemic drug levels - cushingnoid symptoms
Also topical aminoglycosides can lead to permanent hearing loss.
What is the problem with rectal absorption?
Variation in rectal venous drainage leads to erratic absorption
When is rectal absorption useful?
Useful route in patients who are vomiting/NBM or in infants + young children who are reluctant to take oral medication.
But not always popular or convenient.
Describe intravenous administration
- 100% bioavailability - child receives full drug
- Very commonly used
- Problems - access + drug compatibilities (safe to give 2 drugs together?)
What things do we need to consider in drug distribution?
- Sizes of body water compartments
- Plasma protein binding capacity
- Degree of development of BBB
- Metabolic disturbances eg. acidosis
- Drug specificity for tissue receptor sites
What is the volume of body water like in children and adults?
Total body water higher in neonates and young infants and continues to decrease to 60% by 4 months and remains like that.
Their adipose tissue also has more water than lipid
What is needed to achieve steady state in regards to there being higher total body water in young infants?
- May require large loading doses on mg/kg basis to achieve steady state
- Maintenance doses depend on clearance
