Pediatric Drug Doses

Individualization of drug therapy is an essential part of rational therapeutics. Many physiological parameters (total body water creatinine clearance) are related to body surface area there are genetic environmental and other influences that impact on drug disposition in pediatric dose calculations. Differences in pharmacokinetics are most marked in the newborn specially in prematures. Drug elimination in infancy and childhood may equal or even exceed that in adult. All parameters of pharmacokinetic are affected by age. Bioavailability of rifampicin gentamicin phenytoin phenobarbitone naldixic acid and acetaminophen is increased in infancy. Proportionate and dextropropoxyphene exhibit wide inter-individual variability in plasma levels in children. Apparent volume of distribution of gentamicin and kanamycin is at least twice in newborn than in adult. Volume of distribution of ticarcillin is twice in newborn as compared to a child aged 2 years. The newborn has limited capacity for metabolism and a decrease in first order elimination rate is seen for most drugs (phenobarbitone and theophylline) in newborn infants.