Physiological differences between children and adults can cause differences in drug pharmacokinetics.
- Neonates and infants have higher gastric pH, higher gastric motility, and lower level of bile acids which can affect drug absorption.
- Neonates and infants have higher total body water and lower albumin conc which can affect drug distribution and plasma protein binding of drugs.
- The kidney function is not fully developed and the enzymatic capacity is generally lower (sometimes higher) in neonates and infants which can affect the rate of drug elimination.
Theophylline metabolic rate in infants and children is faster than in adults. However, theophylline metabolic rate in premature infants is slower than in adults.
After administration of the same dose of theophylline (adjusted for body weight) the s.s. conc in infants and children will be lower than adults, and in premature infants the s.s. conc will be higher than adults.
The theophylline dose required to achieve conc within the therapeutic range in infants and children is higher than that in adults, while in premature infants the dose is lower than the dose in adults.
