Why must drug doses for infants be different from drug doses for adults?

Drug dosages for infants must differ from those for adults because children are not simply small adults; they possess distinct physiological and anatomical characteristics that significantly alter how their bodies process medication.1

Key factors necessitating these dosage adjustments include:

• Organ Immaturity: Infants have immature liver and kidney functions, which limit their ability to metabolize and excrete certain drugs effectively.12
• Pharmacokinetics: Infants often exhibit different rates of drug absorption due to irregular bowel motility and decreased gastric acidity.1
• Body Composition: Premature infants, in particular, have a higher proportion of body water and less fatty tissue compared to adults, which affects how drugs are distributed throughout the body.13
• Metabolic Rates: Metabolic rates are much higher during childhood, influencing the pharmacokinetics of medications.1

Because of these variations, dosages are typically calculated based on weight (milligrams per kilogram) or body surface area rather than age alone. Adjusting these doses is a critical medical necessity to ensure safety and efficacy, as individual variations in size and development further complicate standard computations.12