ABSTRACT
Intra- and inter-individual variations in drug metabolism and disposition are central to differences in the therapeutic response to a standard dosage regimen. In adults, variability is the result of complex interactions between genetic determinants and the environment. This explains why drug dosage must be adjusted to each patient in order to obtain the required therapeutic effect, while reducing the incidence of adverse effects. Adjusting dosage is particularly important when drugs have a narrow therapeutic range and metabolic variability is high. In children, the variability of drug disposition is even more complex, as the expression of genetic and environmental factors is modified by the impact of the physiological development /maturation [1].
