Developmental Pharmacology

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Dev Pharma Basics - Age & Stages

Developmental pharmacology: Studies drug effects across human development, focusing on how age-related physiological changes impact pharmacokinetics (PK) and pharmacodynamics (PD).

  • Pediatric Age Groups:

    • Neonate: Birth - 28 days
      • Preterm: < 37 weeks gestation
      • Term: 37-42 weeks gestation
    • Infant: 29 days - 1 year
    • Child: 1 year - 12 years
    • Adolescent: 12 years - 18 years
  • Scope Comparison:

    • Pediatric: Focuses on growth, organ system maturation, and unique drug responses in developing individuals.
    • Geriatric: Addresses age-related organ function decline, polypharmacy, and altered drug responses in elderly.

⭐ 'Off-label' drug use (unapproved indication, age, dose, or route) is prevalent in pediatrics due to limited specific drug trials for children; estimates suggest over 50% of drugs prescribed to children are off-label in some settings.

Pediatric PK - Tiny Bodies, Big Changes

ADMENeonate/Infant Changes (vs. Adult)
AbsorptionGastric: ↑pH, ↓emptying. Skin: ↑permeability. IM: ↓erratic.
Distribution↑TBW (75-80%), ↑ECF; ↓Fat; ↓Protein binding (↓albumin, ↓AAG).
MetabolismPhase I (CYP450): ↓activity. Phase II (Glucuronidation): ↓significantly. 📌 "Glucuronidation Gets Going Gradually".
ExcretionGFR: ↓ (~30-40% adult at birth, adult by ~1yr). Tubular function: ↓ (matures by ~1yr).

⭐ Chloramphenicol toxicity ("Grey Baby Syndrome") in neonates is due to deficient glucuronidation (immature UGT enzyme), leading to drug accumulation.

Pediatric PD & Dosing - Kid Doses, Big Impact

  • PD Differences: Variable receptor density & affinity. Paradoxical drug effects (e.g., benzodiazepines causing agitation).
  • Pediatric Dosing:
    • Weight-based (mg/kg) is common.
    • Body Surface Area (BSA)-based for cytotoxic drugs: Mosteller formula $BSA (m^2) = \sqrt{\frac{Ht(cm) \times Wt(kg)}{3600}}$.
  • Common Pediatric ADRs:
    DrugAdverse Drug ReactionAge Restriction/Concern
    AspirinReye's Syndrome<12-15 yrs (viral illness)
    TetracyclinesTeeth discoloration, bone issues<8 yrs
    FluoroquinolonesArthropathy, tendon damage<18 yrs
    SulfonamidesKernicterusNeonates (<2 months)
    ValproateFatal hepatotoxicity<2 yrs (esp. polytherapy)
  • Off-label drug use is prevalent; requires careful monitoring for efficacy and safety.

⭐ Aspirin is contraindicated in children (typically <12-15 years) with suspected viral illness due to the risk of Reye's syndrome.

Geriatric Pharmacology - Golden Years, Gentle Doses

  • Pharmacokinetic (PK) Changes & Implications:
    ParameterChange in ElderlyClinical Implication
    Absorption↓Gastric acid, ↓MotilityVariable absorption
    Distribution↓TBW, ↓Lean mass, ↑Fat, ↓AlbuminAltered Vd, ↑free drug
    Metabolism↓Hepatic flow, ↓Phase I↓Clearance, ↑t½
    Excretion↓GFR (Est. CrCl: $CrCl = \frac{(140-age) \times Wt(kg)}{72 \times SCr(mg/dL)} (\times 0.85 \text{ if female})$)↓Elimination, ↑toxicity risk
  • PD Changes: Altered receptor sensitivity, impaired homeostasis (e.g., baroreceptors).
  • Key Issues: Polypharmacy, prescribing cascade, Beers Criteria (e.g., benzodiazepines, anticholinergics), adherence.

⭐ Benzodiazepines: High risk of falls, fractures, confusion in elderly; key Beers criteria PIM (Potentially Inappropriate Medication).

High‑Yield Points - ⚡ Biggest Takeaways

  • Neonates: Immature hepatic enzymes (e.g., Gray Baby Syndrome) & decreased GFR affect drug handling.
  • Pediatric Vd: Affected by higher total body water, lower body fat, and lower plasma protein binding.
  • Key pediatric contraindications: Sulfonamides (kernicterus), tetracyclines (dental/bone), aspirin (Reye's).
  • Geriatric PK: Reduced renal excretion (GFR ↓) is most consistent; body fat ↑, total body water ↓.
  • Geriatric PD: Increased sensitivity to many drugs; polypharmacy elevates ADR risk (Beers criteria).
  • Elderly hepatic metabolism: Phase I (CYP450) declines more than Phase II (conjugation).

Practice Questions: Developmental Pharmacology

Test your understanding with these related questions

Which of the following statements about hypolipidemic drugs is false?

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Flashcards: Developmental Pharmacology

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_____, when given during the third trimester of pregnancy can lead to floppy baby syndrome.

TAP TO REVEAL ANSWER

_____, when given during the third trimester of pregnancy can lead to floppy baby syndrome.

Benzodiazepines

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