Table 1

Childhood physiological changes influencing pharmacokinetics (PK)

PK processDevelopmental change
InputReduced gastric emptying
Intestinal transit time increased
Transporter expression immature
Intestinal permeability increased
Bioavailability may be increased in neonates
DistributionBody composition

  • ▸ Increased extracellular fluid in neonates

  • ▸ Reduced fat in neonates

  • ▸ Reduced muscle in neonates

  • ▸ Dramatic increase muscle bulk (5–15 years)


Increased blood brain barrier permeability
Reduced α-1 acid glycoprotein and albumen concentrations
EliminationImmature hepatic enzyme systems responsible for clearance
Glomerular filtration and tubular excretion immature

  • Most are complete within the first few years of postnatal life.