Developmental pharmacokinetics.

Physiological differences between children and adults result in age-related differences in pharmacokinetics and drug effect. In neonates and infants, decreased weight-adjusted doses are required because of decreased protein binding, renal excretion, and/or metabolism. For children older than 1 year of age, significantly higher weight-corrected doses compared with adults are needed for drugs eliminated by the cytochrome P450 (CYP) isozymes CYP1A2, CYP2C9, and CYP3A4. In contrast, weight-corrected doses for drugs eliminated by renal excretion or metabolism by CYP2C19, CYP2D6, N-Acetyl-transferase, and UDP glucuronosyltransferase in children are similar to those in adults. Ideally, pharmacokinetic and pharmacodynamic data should be available for all drugs used in children. Because many drugs are not approved for pediatric use, data are often limited, especially for older drugs. Understanding the effects of age on pharmacokinetics can help to determine appropriate pediatric dosing in situations in which there is limited information.