ABSTRACT
Introduction 139 Pharmacokinetics 139 Pharmacodynamics 143 Compartment modelling 145
Population pharmacokinetics 147 Size models 148 References 150
Children are ‘therapeutic orphans’ because there are insufficient well-conducted pharmacokinetic (PK) and pharmacodynamic (PD) studies. In their stead there is extrapolation from adult or animal data. Neonates, infants and children are different from adults. Paediatric responses to drugs are determined by a large number of factors, which may change independently during development. Growth and developmental aspects account for major changes in infants and small children whereas body size accounts for most of the pharmacokinetic differences between older children and adults. The pharmacodynamic factors that may influence response in early life remain poorly defined.
