Why are certain age bands used for children in paediatric studies of medicines?

Rational prescribing of medicines requires evidence from clinical trials on efficacy, safety and the dose to be prescribed, based on clinical trials. Regulatory authorities assess these data and information is included in the approved summary of product characteristics. Regulatory guidelines on clinical investigation of medicinal products in the paediatric population generally propose that studies are done in defined age groups but advise that any classification of the paediatric population into age categories is to some extent arbitrary or that the age groups are intended only as a guide. The pharmaceutical companies tend to plan their studies using age groups the regulatory guidelines suggest, to avoid problems when applying for marketing authorisation. These age bands end up in the paediatric label, and consequently into national paediatric formularies. The age bands of the most commonly used age-subsets: neonates, infant/toddlers, children and adolescents, are more historical than based on physiology or normal development of children. Particularly problematic are the age bands for neonates and adolescents. The age of 12 years separating children from adolescents, and the upper limit of the adolescents set by the definition of paediatric age in healthcare, which varies according to the region, are particularly questionable. Modern pharmacometric methods (modelling and simulation) are being increasingly used in paediatric drug development and may allow assessment of growth and/or development as continuous covariables. Maybe time has come to reconsider the rational of the currently used age bands.