Dexamethasone Dosing for Croup in a 38 kg Child
For a 38 kg child with croup, administer 6 mL of dexamethasone (0.6 mg/kg × 38 kg = 22.8 mg, but capped at the maximum dose of 16 mg = 4 mL), given as a single dose orally, intramuscularly, or intravenously. 1
Dose Calculation
- Standard recommended dose: 0.6 mg/kg as a single dose 1, 2, 3
- Calculation for 38 kg child: 0.6 mg/kg × 38 kg = 22.8 mg
- Maximum dose cap: 16 mg 1
- Volume to administer: 16 mg ÷ 4 mg/mL = 4 mL (using the maximum dose)
Route of Administration
- Oral route is preferred when the child can tolerate it—equally effective as intramuscular administration and less invasive 1, 4
- Intramuscular route is reserved for children who are vomiting or in severe respiratory distress unable to tolerate oral medication 4
- Intravenous route can be used if IV access is already established 1
Clinical Considerations
Onset and Duration
- Onset of action: As early as 30 minutes, with statistically significant benefit by 30 minutes 5
- Duration of action: 24-72 hours from a single dose 1
- No tapering required: Single-dose regimen does not cause significant adrenal suppression and requires no taper 1
Severity-Based Management
- Moderate to severe croup: The 0.6 mg/kg dose (maximum 16 mg) is well-established and universally recommended 1, 2, 4
- Adjunctive therapy for severe cases: Consider nebulized epinephrine (0.5 mL/kg of 1:1000 solution, maximum 5 mL) for significant respiratory distress while waiting for dexamethasone to take effect 6, 7
- Racemic epinephrine alternative: If unavailable, L-epinephrine (1:1000) can substitute at 0.5 mL/kg up to 5 mL 7
Common Pitfalls to Avoid
- Do not use lower doses for moderate-to-severe croup: While 0.15 mg/kg may work for mild croup, the 0.6 mg/kg dose is the established standard for moderate-to-severe disease 2, 4
- Do not exceed the maximum dose: Despite the calculated dose being 22.8 mg, cap at 16 mg maximum 1
- Do not delay treatment: Dexamethasone works faster than previously thought (30 minutes vs. the older 4-6 hour estimate), so early administration is beneficial 5
- Monitor for rebound if epinephrine used: Children receiving nebulized epinephrine need at least 2 hours of observation for potential rebound airway obstruction 2