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Table 2. The effect of paediatric physiology on pharmacokinetics of common drugs .

Drug Pharmacokinetic differences Effect
Gentamicin Volume of distribution decreases throughout childhood along with percentage of total body water Higher mg/kg doses used in younger children to ensure therapeutic peaks
Codeine Conversion to morphine difficult to predict along with reduced clearance Accumulation more likely. Not recommended for children due to safety concerns
Theophylline Increased clearance Higher mg/kg doses required in infants and children
Phenytoin Decreased oral absorption due to high stomach pH and decreased protein binding in infants Decreased bioavailability, however lower serum concentrations required due to lower protein binding
Benzyl alcohol (common excipient) Decreased clearance Accumulation in infants leading to fatal ‘gasping syndrome’
Levetiracetam Increased clearance Higher mg/kg dose required in patients up to 12 years of age
Methylphenidate Decreased clearance Lower dose required in children (6–12 years) compared to adolescents