B41 - prescribing in children

Question 1

6 challenges with prescribing in children

Answer 1

No standard dose as with adults
Doses vary with age/weight/body surface area
Uncertainty regarding allergy status
Drugs often used off-licence
Differences in physiology affecting drug handling
More severe consequences of side effects or drug errors

Question 2

Indications for antibiotics in otitis media

Answer 2

systemically unwell, risk of complications, otorrhoea, <2 years with bilateral infection

Question 3

antibiotic regime in otitis media

Answer 3

Prescribe a 5–7 day course of amoxicillin.
For people who are allergic to, or intolerant of,penicillin, prescribe a 5–7 day course of clarithromycin or erythromycin

Question 4

Pros/cons of paracetamol for analgesia in children

Answer 4

Usually preferred for mild to moderate pain
Minimal side effects
Dangerous in overdose

Question 5

Pros/cons of NSAIDs for analgesia in children

Answer 5

Useful for chronic disease with pain and inflammation
Troublesome side effects
Be aware of cautions and contra-indications

Types of pain responding better to an NSAID includes soft-tissue injury, tissue compression, visceral pain caused by pleural/peritoneal inflammation and bone pain. Indications for NSAIDs include inflammatory conditions, post-operative pain, headache and primary dysmenorrhoea.

Question 6

Prescribing aspirin in children

Answer 6

Should never be prescribed in children under 16

Except in Kawasaki disease or when used specifically for its antiplatelet action

Question 7

Reye’s syndrome

Answer 7

Rare
Usually occurs in children between 5 and 14 years of age
Acute encephalopathy and fatty degeneration of the liver
Usually follows viral illness, with rapid deterioration
Overall mortality rate ~ 20%
Associationed with use of aspirin

Question 8

Analgesia ladder in children

Answer 8

Slight: Paracetamol
Mild: Paracetamol + NSAID
Severe: Paracetamol + NSAID + opioid

Question 9

4 factors affecting absorption of oral drugs in neonates/infants

Answer 9

Variable gastric transit time (<6-8 months)
Gastric pH - neutral at birth, higher pH -> increased absorption of weak base drugs e.g. penicillin - lower doses of basic drugs and higher doses acidic required
Decreased bile acid secretion - reduced fat absorption and fat soluble drugs (e.g. diazepam)
Decreased bowel length (<4 months) - reduced effective absorptive surface

Question 10

2 phases of hepatic drug metabolism

Answer 10

Phase I alters the structure of the drug and is performed by the cytochrome P450 system. The processes include oxidation, reduction, demethylation and hydrolysis.

Phase II allows conjugation with another molecule, usually to make it water soluble. The process include acetylation, sulphanation, glucuronidation and glycine conjugation.

Question 11

hepatic metabolism in children

Answer 11

The enzymes require for metabolism mature at different rates and hepatic drug clearance is low

Question 12

Implications of prescribing chloramphenicol in children

Answer 12

the enzyme required to metabolise the drug is not active in neonates resulting in a build up of chloramphenicol. This can lead to grey-baby syndrome resulting in circulatory collapse, cyanosis and abdominal distension. Therefore, only used in neonates in life-threatening infections

Question 13

explain differences in risk of paracetamol overdose between neonates and adults

Answer 13

In adults paracetamol metabolised by cytochrome P450 and produces a toxic metabolite which is neutralised by glutathione, also metabolised by glucuronidation. In overdose these processes are saturated and stores of glutathione are depleted, resulting in a build up of toxic metabolites.

In neonates CYP450 is immature so paracetamol is not metabolised via this route, resulting in less toxic metabolites and lower risk in overdose. Instead, the predominate pathway is via sulphation.