Reviewed by Shameer Deen, ST5 Urology Registrar
Paediatric prescribing is one of the most error-prone areas of clinical medicine. Children are not simply small adults — their physiology, pharmacokinetics, and drug handling change dramatically from the neonatal period through to adolescence [1]. Getting the dose right is critical, and the consequences of error can be severe.
Why Paediatric Dosing Is Different
Several physiological factors make drug handling in children fundamentally different from adults [1,3]:
- Body composition — neonates have a higher proportion of body water and lower body fat, affecting the volume of distribution of water-soluble and lipid-soluble drugs differently [3]
- Hepatic metabolism — CYP enzyme systems mature at different rates; some are fully active at birth while others take months to reach adult levels [1]
- Renal clearance — glomerular filtration rate does not reach adult levels until approximately 12 months of age [3]
- Protein binding — neonates have lower albumin levels, leading to higher free drug fractions and increased pharmacological effect [1]
Weight-Based Dosing: The Foundation
Most paediatric drug doses are calculated on a mg/kg basis [2]. This seems straightforward, but several pitfalls exist. First, always use the actual measured weight rather than an estimated or historical weight. Second, be aware that weight-based calculations can sometimes exceed the maximum adult dose — always cap at the adult ceiling. Third, for obese children, ideal body weight may be more appropriate for certain drugs.
MedNext Formulary includes 11 built-in dosing calculators that perform these calculations instantly, including age and weight-based adjustments. The calculators run entirely on-device with no network dependency, so they work even in areas with limited connectivity.
Age-Specific Considerations
Drug choice and formulation must be tailored to the child's age [2]:
- Neonates (0-28 days) — extremely sensitive to drug accumulation; many drugs require extended dosing intervals [1]
- Infants (1-12 months) — rapid growth means doses need frequent recalculation; liquid formulations are essential
- Young children (1-5 years) — liquid or dispersible formulations preferred; palatability affects adherence
- Older children (6-11 years) — may manage tablets; dose often needs individualising between paediatric and adult ranges
- Adolescents (12-17 years) — pharmacokinetics approach adult values, but emotional and cognitive development affects adherence [3]
Common Errors in Paediatric Prescribing
The most frequent paediatric prescribing errors include tenfold dose errors (often from misplacing a decimal point), confusion between mg and mL in liquid preparations, failure to account for concentration differences between formulations, and using adult doses without adjustment [2]. Each of these is preventable with careful calculation and verification.
Using MedNext for Paediatric Prescribing
MedNext Formulary includes a dedicated paediatric formulary with 1,066 drug monographs from the MedNext Proprietary Clinical Dataset. Each monograph includes age-specific dosing guidance, formulation information, and safety alerts. Combined with the built-in dosing calculators, MedNext provides a robust safety net for paediatric prescribers at every level of experience.
References
- Kearns GL, Abdel-Rahman SM, Alander SW, Blowey DL, Leeder JS, Kauffman RE. Developmental Pharmacology—Drug Disposition, Action, and Therapy in Infants and Children. N Engl J Med. 2003;349(12):1157-1167.
- Royal College of Paediatrics and Child Health. Medicines for Children. RCPCH, 2024.
- Fernandez E, Perez R, Hernandez A, Tejada P, Arteta M, Ramos JT. Factors and Mechanisms for Pharmacokinetic Differences between Pediatric Population and Adults. Pharmaceutics. 2011;3(1):53-72.