Pediatric Pharmacology

Introduction — "children are not small adults"

• Definition & scope — Paediatric pharmacology studies how drugs are handled by, and act upon, the developing human from birth through adolescence — a continuum in which absorption, distribution, metabolism, excretion (ADME) and pharmacodynamic responsiveness change with age rather than remaining fixed.
• The cardinal axiom — "infants and children are not small adults" — they have important physiological differences from adults, so paediatric doses and intervals must be learned as such and not derived from any formula scaled down from the adult dose; age-based formulae "are not in use now."
• Two reasons it is a distinct discipline — (a) developmental pharmacokinetics — organs that clear drugs (kidney, liver) mature postnatally on their own timetable; and (b) developmental vulnerabilities — immature handling exposes specific organs (brain, marrow, growing bone/teeth/epiphyses) to toxicities not seen in adults.
• The neonate is the extreme — the neonate and premature infant sit at the extreme of this spectrum — defects of immature elimination "are exaggerated in the premature infant," making individualization most critical here.
• Dosing strategy — children inherit the general framework — standard, regulated, target-level (TDM-guided) and titrated dosing — but for narrow-window drugs in neonates the target-level/TDM strategy dominates, because immature clearance makes the plasma level unpredictable from dose alone.