Clinical meaning
Pediatric pharmacokinetics differ significantly from adults due to developmental changes in body composition and organ maturation. Neonates have higher total body water (75-80% vs 55-60% in adults), increasing the volume of distribution for hydrophilic drugs (aminoglycosides, vancomycin require higher mg/kg doses). Lower protein binding (reduced albumin and alpha-1 acid glycoprotein) increases free drug fraction. Hepatic drug metabolism develops at different rates: phase I reactions (CYP450 oxidation) mature by 6 months to 2 years, while phase II conjugation (glucuronidation) matures by 3-4 years (chloramphenicol toxicity in neonates from immature glucuronidation = gray baby syndrome). Renal glomerular filtration rate reaches adult values by 6-12 months but is only 25-30% of adult GFR at birth. Drug dosing errors are the most common and preventable adverse events in pediatrics, with 10-fold dosing errors being particularly lethal. The Broselow tape estimates weight-based dosing from length in emergency situations.
Diagnosis & workup
Diagnostics & workup: - Obtain accurate daily weight in kilograms (verify decimal placement) - Calculate dose using verified weight: mg/kg/dose or mg/kg/day divided by frequency - Cross-reference calculated dose against maximum adult dose - Verify concentration of liquid formulations (multiple concentrations exist for many pediatric medications) - Use Broselow tape for length-based dosing in emergencies when weight unknown - Monitor drug levels for narrow therapeutic index medications (gentamicin, vancomycin, phenytoin)