31. Pharmacology Flashcards
What should you do when prescribing for kids?
BNF C
don’t just ask a mate- Malay will get you
Why are drug interactions different in kids?
Affected by age, size, nutrition and growth
Especially true for neonates, physiological variables change rapidly
What are the hardest children to treat with the drugs
The younger the worse
What classes of mother drugs can affect children?
Beta blockers- seizures
Opioids- dependence
Breast milk can transfer drugs from mother to child
What are the principles in prescribing for children?
Use the simplest dose
Pay attention to route, formulation and duration of therapy
Always check BNFc
What is phacomelia?
A lack of limb development due to thalidomide toxicity in children
What are the new criteria set after the thalidomide crisis?
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
What is the difference between adult and chid drug prescribing?
Major pharmacokinetic differences
Altered pharmacodynamic response
Effects on growth and development not known
Different specific pathologies
What can be said about medicines used in children?
70% of medicines have never been studied in children
Many medicines are used off label (unlicensed)
What are unlicensed medicines?
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
Give some examples of off label prescribing
Changing medium
Medicines used for an indication not intended
Medicines used at a different dose
Medicines only being used in clinical trials
How common is off label prescribing?
Neonates 60-90%
Children 10-15% in hospital,
30% in the community
What is the problem of using off label drugs?
No evidence of efficacy, ADR’s and toxicity
What happens to drug clearance in children?
Clearance increases till puberty
At puberty it drops by around 15%. This leads to increased toxicity during puberty
What are the problems with paroxetine?
SSRI, when used in children there is a 4 fold increase in suicide
What is the problem with oral administration of medication?
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
What are the differences of skin absorption in children?
Enhanced in infants and children, especially with damaged skin
What are the differences of rectal absorption in children?
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.
How is renal excretion changed in children?
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
How does the liver affect metabolism?
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
Summarise the big differences between neonates and children?
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
