Dexamethasone Dosing for Croup in a 4-Year-Old Child Weighing 40 Pounds
Administer a single dose of dexamethasone 0.6 mg/kg (maximum 16 mg) orally, which for this 40-pound (18 kg) child equals approximately 11 mg. 1, 2
Dose Calculation
- Weight conversion: 40 pounds = 18.2 kg
- Calculated dose: 0.6 mg/kg × 18.2 kg = 10.9 mg (round to 11 mg)
- Maximum dose cap: 16 mg (not applicable for this child) 1, 2
Route of Administration
- Oral administration is preferred when the child can tolerate it, as it is equally effective as intramuscular or intravenous routes and avoids the pain of injection 1, 2
- All three routes (oral, IM, IV) demonstrate equal efficacy for croup treatment 2
Expected Clinical Response
- Onset of action: As early as 30 minutes after administration 1, 2
- Duration of action: Approximately 24-72 hours, providing sustained relief 1, 2
- No tapering required: The single-dose regimen does not cause significant adrenal suppression 1
Adjunctive Therapy for Severe Cases
If this child presents with moderate to severe croup (prominent stridor, significant retractions, agitation):
- Add nebulized epinephrine while waiting for dexamethasone to take effect 2, 3
- Epinephrine dose: 0.5 mL/kg of 1:1000 solution (maximum 5 mL) = approximately 9 mL for this 18 kg child, capped at 5 mL maximum 2, 3
- Epinephrine provides immediate but short-term relief, while dexamethasone provides longer-lasting benefit 1, 2
Repeat Dosing Considerations
- For severe croup requiring repeat treatment: Administer another dose of dexamethasone plus nebulized epinephrine regardless of timing of the initial dose 1
- Children requiring two epinephrine treatments should be hospitalized 4
Important Clinical Caveats
- Do not use nebulized corticosteroids from hand-held inhalers with spacers—they are ineffective for croup 1
- Dexamethasone is specifically indicated for croup (laryngotracheobronchitis), characterized by the classic "seal-like barking cough" 2
- The evidence demonstrates that even lower doses (0.15 mg/kg) may be effective 5, 6, 7, but the standard recommended dose remains 0.6 mg/kg per American Academy of Pediatrics guidelines 1, 2