Zithromax (Azithromycin) Dosing for Children
For most pediatric infections, azithromycin is dosed at 10 mg/kg (maximum 500 mg) on day 1, followed by 5 mg/kg (maximum 250 mg) once daily on days 2-5, which is the preferred regimen for community-acquired pneumonia and atypical infections. 1, 2, 3
Standard Dosing Regimens by Indication
Community-Acquired Pneumonia (Preferred Indication)
- 5-day regimen: 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg (max 250 mg) daily for days 2-5 1, 2, 3
- This is the preferred regimen for atypical pathogens (Mycoplasma pneumoniae, Chlamydia trachomatis, Chlamydophila pneumoniae) 1, 2
- For severe cases requiring IV therapy: 10 mg/kg IV on days 1-2, then transition to oral 1
Acute Otitis Media
You have three FDA-approved options 3:
- 5-day regimen: 10 mg/kg day 1, then 5 mg/kg days 2-5 (same as pneumonia dosing)
- 3-day regimen: 10 mg/kg once daily for 3 days
- Single-dose regimen: 30 mg/kg as a single dose (maximum 1500 mg)
The 3-day and 5-day regimens show comparable efficacy (95.7% vs 96.1% cure rates) 4, though the single-dose regimen may have slightly lower success rates against H. influenzae (77%) compared to S. pneumoniae (91%) 5.
Acute Bacterial Sinusitis
- 3-day regimen: 10 mg/kg once daily for 3 days 3
Pharyngitis/Tonsillitis
- Higher dose required: 12 mg/kg once daily for 5 days (ages ≥2 years) 2, 3
- This higher dose is necessary because standard dosing results in more recurrences compared to penicillin 6
Pertussis (Treatment and Prophylaxis)
- Infants <6 months: 10 mg/kg once daily for 5 days 2
- Children ≥6 months: 10 mg/kg day 1, then 5 mg/kg days 2-5 2
- Azithromycin is preferred over erythromycin in young infants due to better safety profile and no association with infantile hypertrophic pyloric stenosis 2
Weight-Based Dosing Tables
For 5-Day Pneumonia/Otitis Regimen 3:
- 5 kg (11 lbs): 2.5 mL day 1, then 1.25 mL days 2-5 (using 100 mg/5 mL suspension)
- 10 kg (22 lbs): 5 mL day 1, then 2.5 mL days 2-5
- 20 kg (44 lbs): 5 mL day 1, then 2.5 mL days 2-5 (using 200 mg/5 mL suspension)
- 30 kg (66 lbs): 7.5 mL day 1, then 3.75 mL days 2-5
- ≥50 kg (≥110 lbs): 12.5 mL day 1, then 6.25 mL days 2-5 (adult dose: 500 mg/250 mg)
Alternative Weight-Based Dosing (Once Daily) 2:
- 15-25 kg: 200 mg once daily
- 26-35 kg: 300 mg once daily
- 36-45 kg: 400 mg once daily
- ≥46 kg: 500 mg once daily
Important Clinical Considerations
Administration
- Can be taken with or without food 3
- Do not administer with aluminum- or magnesium-containing antacids, as they reduce absorption 2
- If vomiting occurs within 30 minutes of single-dose (30 mg/kg) administration, re-dosing at the same dose is acceptable 3
Safety Profile
- Generally well-tolerated with mild-to-moderate gastrointestinal side effects (5-7% incidence) 4, 7
- Better tolerated than amoxicillin/clavulanate (0% vs 15% adverse events) 7
- Common side effects: abdominal discomfort, diarrhea, nausea, vomiting 2
- Monitor for QT prolongation when used with other QT-prolonging medications 2
Resistance Considerations
- Clinical success with macrolide-susceptible S. pneumoniae: 90% 5
- Clinical success with macrolide-resistant S. pneumoniae: 67% (p=0.01) 5
- In areas with high macrolide resistance, consider alternative agents or higher doses 5