Safe Prescribing in Children Flashcards
1
Q
Why is paediatrics a high risk prescribing area?
A
- Children are not small adults with respect to pharmacokinetics and pharmacodynamics of drugs.
- More prone to drug errors which can have serious consequences.
- Often have to manipulate adult formulations due to lack of syrups etc on market.
- Licencing issues – may not be licenced for use in children therefore potential lack of evidence for safe use.
- Calculations galore!
- Missed doses are a common problem due to poor adherence.
2
Q
What are the common problems with calculations when prescribing for children?
A
- 10 fold and 100 fold overdoses common.
- mg/Kg dose confused with mg/Kg/day.
- Confusion between doses expressed as mgs or mLs.
- Confusion between units as often dealing with much smaller doses - milligrams/ micrograms/ nanograms.
3
Q
Define the following terms:
- Neonate
- Infant
- Child
- Adolescent
A
4
Q
What are the legal issues surrounding licensing in paediatric prescribing?
A
- Medicine may be:
- Licensed but not for use in children.
- Licensed in children but used outwith the license - this is ‘off-label’ prescribing.
- Not licensed in the UK.
- Prescribing unlicensed medicines or medicines outside their marketing authorisation alters (and probably increases) the prescriber’s professional responsibility and potential liability.
- The prescriber must be able to justify and feel competent in using such medicines in that particular age group or condition.
5
Q
Describe how absorption varies according to route of administration in children.
A
-
Oral
- At birth – 3 years : reduced gastric acids, increased gastric emptying. Leads to e.g. Increased oral absorption of penicillins and reduced oral absorption of phenobarbitone, phenytoin, rifampicin in infants.
- Over 3 – similar to adults.
-
Intramuscular
- Erratic absorption.
- Painful due to small muscle mass.
- Tends to be ineffective in neonates.
- Not to be used for convenience.
- Needle phobia common.
-
Intravenous
- Requires extreme care with dilutions and calculations, need to bear in mind displacement values of drugs.
- Extravasation risk.
- Needle phobia common in children.
-
Percutaneous (topical)
- Enhanced absorption in infants due to:
- Thinner skin, better hydrated, increased surface area.
- May be harmful as more drug absorbed - eg steroids, chlorhexidine – increased side-effects.
-
Rectal
- Variation in blood supply to rectum – may yield variable response.
- Useful in vomiting or if reluctant to take.
- Useful for some drugs like diazepam, paracetamol.
-
Buccal
- Good route for some drugs as doesn’t require swallowing e.g. midazolam.
6
Q
What are the factors which affect drug distribution in children?
A
- The two main factors influencing drug distribution are body composition and plasma protein binding.
- Protein binding reduced
- Volume of distribution increased
- Result? This may affect the therapeutic window for a drug (i.e. the level in which to aim for of the drug in the body which maximises efficacy and safety).
- Examples:
- Phenytoin therapeutic window lower in neonates.
- Greater doses of water soluble drugs (Penicillin, Gentamicin) on weight / weight basis in newborns.
7
Q
How does body composition affect drug distribution in children?
A
- Extracellular fluid is much higher in newborn infants (45%).
- It decreases gradually with increasing age - 25% at 1 year, and 20% by adulthood.
- This means greater doses of water-soluble drugs e.g. penicillin and aminoglycosides on a weight to weight basis are required.
- For example the normal dose of IV Flucloxacillin for a premature neonate is 25mg/kg. If you were to give this to a 70kg adult the dose would be 1.75g but the usual adult dose is a wide range between 0.25g – 2g.
8
Q
How does protein binding affect drug distribution in children?
A
- In premature neonates, plasma protein binding is reduced resulting in higher concentrations of free (active) drug.
- This is due to reduced levels of circulating proteins and a reduced ability to bind.
- Therefore these patients have a higher apparent volume of distribution than adults.
- Therapeutic window for phenytoin is lower in neonates than older children due to increased free phenytoin as a proportion of the whole plasma level (aiming for therapeutic level between 6-15mg/L rather than 10-20mg/L).
9
Q
Describe drug metabolism in children (pre-term and newborns and also older children).
A
-
Pre-term and newborns have decreased rates of hepatic metabolising capacity due to immature enzyme systems in the liver, particularly oxidation and glucuronidation. This can increase the half-life of some drugs and cause worse side-effects.
- e.g. Increased half-life of diazepam in neonates means it will take longer to excrete so increases side-effect profile.
- Older children (aged 1-9yrs) have greater hepatic metabolising compacity than adults.
- This is thought to be due to the fact that, relative to body size, the liver is larger in children than in adults.
- e.g. theophylline and most anti-epileptics require a larger dose per kilogram than adults to achieve therapeutic plasma concentrations.
- These differences make it difficult to predict correct doses and frequencies of drugs so must be assessed and reviewed frequently to be patient-centered.
10
Q
Describe drug elimination in the neonate.
A
- The neonatal liver and kidneys are immature in their capacity to eliminate drugs.
- Both hepatic metabolism and kidney function are reduced in premature babies resulting in increased plasma half-lives of both hepatically and renally cleared drugs.
- This leads to longer plasma half-lives and increased plasma drug concentrations.
- The elimination of a drug from the body is often the most important indices for dosing, so if there is organ (renal or liver) immaturity or impairment there is usually a need to:
- decrease dose OR
- increase dosing interval
11
Q
What is the advice for prescribing for children with renal impairment.
A
- Avoid nephrotoxic drugs.
- Examples of problem drugs:
- Opiates
- NSAIDs
- ACE-I
- Immunosuppressants
- Gentamicin
- Creatinine levels change with age, weight and muscle mass and are more difficult to interpret.
- Look at trends for serum creatinine.
- Use local lab references.
- Equation in BNFC to estimate creatinine clearance but consult specialist immediately if impairment is suspected.
- Monitor for symptoms and signs of kidney injury - e.g. oliguria, nephritis, hypoperfusion.
12
Q
What is the advice for prescribing for children with hepatic impairment?
A
- Avoid hepatotoxic drugs.
- Problem drugs:
- sedatives
- opioids
- diuretics
- amphotericin
- anticoagulants
- In hypoproteinaemia – extra care with protein bound drugs (e.g. Phenytoin, prednisolone, warfarin, benzodiazepines).
13
Q
What are the other ‘alarm bell’ drugs in paediatrics?
A
- Tetracyclines (e.g. doxycycline) – avoid in under 12 years of age – deposited in growing bone and teeth, by binding to calcium, causes staining and occasionally dental hypoplasia).
- Systemic chloramphenicol causing “grey baby syndrome” in newborns if dosing too high.
- Aspirin associated with Reye’s syndrome, not licenced if 16 years of age and under.
14
Q
What are the considerations when prescribing by the oral route for children?
A
- Young children find it difficult to swallow tablets or capsules so liquid preparations are usually first choice.
- Use paediatric formulations where available.
- Flavourings, colourings or preservatives may be allergenic.
- Check if child is lactose intolerant, as this is a common excipient in medicines.
- Choose sucrose and alcohol-free (e.g. Phenobarbitone solution - this is alcohol free; whereas elixir contains 38% alcohol).
- Taste, colour and smell? These all affect adherence.
- Different brands may need to be tried depending on if it is strawberry or banana flavour!
- Juice / yoghurt can help mask tastes but drugs should only be added to small quantities of food / drink.
- E.g. added to a teaspoon of yoghurt, not a carton as full dose may not be taken.
- Never add drugs to feeding bottle.
15
Q
What are the problems with excipients?
A
16
Q
What are the safe paediatric prescribing principles?
A
