Dexamethasone Dosing for Croup in Adults
Adults with croup should receive dexamethasone 0.6 mg/kg (maximum 10-12 mg) as a single dose, administered either orally or intramuscularly, based on the established pediatric evidence which can be extrapolated to adults given the identical pathophysiology of the disease. 1
Dosing Algorithm
Standard Dose
- 0.6 mg/kg as a single dose (maximum 10-12 mg) is the most widely studied and recommended dose for moderate-to-severe croup 1, 2
- This dose has become the standard of care based on decades of evidence showing reduced hospitalizations, shorter illness duration, and decreased need for subsequent treatments 1
Route Selection
- Oral administration is preferred when the patient can tolerate it, due to ease of administration, availability, and equivalent efficacy to intramuscular dosing 1, 3
- Intramuscular administration should be reserved for patients who are vomiting or in severe respiratory distress unable to tolerate oral medication 1
- Oral and IV dexamethasone have 1:1 bioequivalence, so the same dose applies regardless of route 4
Lower Dose Considerations
- 0.15 mg/kg may be equally effective for moderate-to-severe croup, as demonstrated in multiple randomized trials showing no difference in croup scores, hospitalization duration, or need for additional interventions compared to 0.6 mg/kg 2, 5, 6
- The 0.15 mg/kg dose (maximum 3 mg) could be considered for mild disease or when minimizing steroid exposure is desired 1, 6
Evidence Strength and Nuances
The evidence base for croup treatment is predominantly pediatric, but the pathophysiology of laryngeal inflammation is identical in adults, making extrapolation appropriate. Multiple high-quality randomized controlled trials have established that:
- 0.6 mg/kg versus 0.15 mg/kg showed no statistical difference in time to symptom resolution (8 hours vs 7.9 hours), croup scores at any time point, or need for intubation 5
- 0.15 mg/kg, 0.3 mg/kg, and 0.6 mg/kg all produced similar outcomes in hospitalization duration and symptom reduction 6
- Oral versus intramuscular administration showed equivalent efficacy with 51% complete resolution in both groups and no difference in need for subsequent interventions 3
Adjunctive Treatment
- Nebulized epinephrine (racemic or L-epinephrine) should be administered concurrently for acute airway edema: 0.5 mL of racemic epinephrine 2.25% solution (or 5 mL of 1:1000 L-epinephrine) in 2 mL normal saline via nebulizer 7
- Dexamethasone works synergistically with epinephrine, with steroids providing sustained benefit while epinephrine provides rapid but temporary relief 5
Common Pitfalls to Avoid
- Do not withhold dexamethasone in mild croup - evidence suggests benefit even in self-limiting disease, though lower doses (0.15-0.3 mg/kg) may be appropriate 1
- Do not use multiple doses - a single dose is sufficient for most cases of croup 1, 3
- Do not confuse croup dosing with other indications - the 0.6 mg/kg dose for croup is much lower than the 40 mg used for immune thrombocytopenic purpura 8
- Corticosteroid-induced complications are rare with single-dose therapy, with the only significant concern being increased risk of severe varicella infection in exposed patients 2