Paediatrics respond to medicines very differently from adults, especially newborns and infants. Their bodies absorb, distribute, metabolize, and eliminate drugs differently. Because of this, special care is required to choose the correct medicine, the correct formulation, and the correct dose.
Factors Affecting Drug Disposition in Paediatrics
1. Oral Absorption
- Gastric emptying is slow in young infants and matures by 6 months.
- Gastric acidity is low until around 2 years of age.
- Intestinal movement may be faster in older infants.
- Food content, posture, diseases, and co-administered drugs can affect absorption.
2. Distribution
- Newborns have higher total body water → need higher mg/kg doses for water-soluble drugs.
- Plasma protein binding is lower because of low albumin and globulin levels.
- High bilirubin in neonates can displace drugs from albumin.
3. Metabolism
- Different liver enzymes mature at different ages; some are absent or low at birth.
- Children may have different metabolic pathways for certain drugs.
- Metabolic rate is often higher than adults → may need more frequent dosing.
4. Excretion
- Kidney function matures fully by 6–8 months.
- Reduced renal clearance in neonates affects drug elimination.
Route of Administration & Drug Regimens
- Compliance depends on taste, appearance, and ease of administration.
- Schedules should match the child’s daily routine; avoid school-time doses when possible.
- If school dosing is required, provide separately labelled containers.
- Many schools require written parental permission for giving medicines.
- Avoid painful intramuscular injections when possible.
Product Licensing
- Prefer prescribing medicines within product licence limits.
- Many paediatric uses require off-label or unlicensed prescribing — acceptable when evidence supports safety and benefit.
- Doctors must ensure adequate information exists before prescribing off-label.
- The Medicines Act allows use of unlicensed medicines when needed.
Prescription Writing
- Age must be written for children under 12 — but it is best to include age for all paediatric prescriptions.
- State strength of tablets/capsules clearly.
- Sugar-free liquids are preferred for long-term use to prevent dental caries.
- Children able to swallow tablets may prefer solid dosage forms.
- Doses less than 5 mL are dispensed with an oral syringe.
- Parents should not mix medicines with milk or food — dosage becomes uncertain.
Dosages
- Paediatric patients are not “small adults”; doses must come from reputable paediatric references.
- Age categories: Preterm (<37 weeks), Neonate (0–1 month), Infant (1–24 months), Child (2–12 years), Adolescent (12–18 years).
- The term “child” in BNF means ≤12 years unless stated otherwise.
Dose Calculation
- Doses may be calculated using age, weight, body surface area (BSA), or combinations.
- BSA methods are more accurate than weight-based dosing.
- mg/kg dosing must consider children’s higher metabolic rates.
- In overweight children, actual weight may give too high a dose → use ideal body weight.
- BSA can be calculated using height and weight via nomograms or calculators (e.g., Boyd formula).
Adverse Drug Reactions (ADRs) in Paediatrics
ADRs in children may differ from adults due to different pharmacokinetics and developmental physiology.
- Many drugs are not thoroughly tested in children.
- Off-label use is common due to lack of paediatric formulations.
- Illness patterns differ in children, affecting ADR presentation.
- Suspected ADRs must be reported to the MHRA, even for off-label or unlicensed use.
Safety in the Home
- Medicines must always be stored out of children’s reach.
- Use child-resistant containers unless inappropriate or specifically requested otherwise.
- Solid and liquid oral medicines must be dispensed in child-resistant packaging unless exceptions apply.
Detailed Notes:
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