Azithromycin Dosing for Pediatric Patients
For most pediatric infections, azithromycin should be 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. 1, 2
Standard Dosing by Indication
Community-Acquired Pneumonia (Atypical Pathogens)
- 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg (max 250 mg) daily for days 2-5 3, 1, 4
- This 5-day regimen is recommended by both the Infectious Diseases Society of America and the American Academy of Pediatrics for atypical pneumonia caused by Mycoplasma pneumoniae, Chlamydia pneumoniae, or Chlamydia trachomatis 3, 1
- Critical caveat: Azithromycin is NOT first-line for typical bacterial pneumonia caused by S. pneumoniae or H. influenzae—amoxicillin remains the preferred agent for these pathogens 3, 2
Acute Otitis Media
The FDA label provides three acceptable regimens 4:
- 30 mg/kg as a single dose (1-day regimen)
- 10 mg/kg once daily for 3 days (3-day regimen)
- 10 mg/kg on day 1, then 5 mg/kg daily for days 2-5 (5-day regimen)
Pharyngitis/Tonsillitis (Group A Streptococcus)
- 12 mg/kg once daily for 5 days (maximum 500 mg/day) 2, 4
- This higher dose is necessary because the standard 10 mg/kg regimen results in unacceptably high recurrence rates for streptococcal pharyngitis 5
- Research demonstrates that 20 mg/kg/day for 3 days achieves bacteriologic eradication rates comparable to penicillin V (94.2% vs 84.2%), while 10 mg/kg/day for 3 days is inadequate (57.8% eradication) 5
- Important limitation: Azithromycin is second-line therapy for strep throat—penicillin or amoxicillin remain first-line 3
Acute Bacterial Sinusitis
- 10 mg/kg once daily for 3 days 4
Pertussis (Treatment and Prophylaxis)
- Infants <6 months: 10 mg/kg once daily for 5 days 1
- Children ≥6 months: 10 mg/kg (max 500 mg) on day 1, then 5 mg/kg (max 250 mg) daily for days 2-5 1
- Azithromycin is the preferred macrolide for infants under 1 month due to superior safety profile compared to erythromycin 1
Weight-Based Dosing Table (5-Day Regimen)
For the standard 5-day regimen using oral suspension 4:
| Weight | Day 1 Dose (200 mg/5 mL) | Days 2-5 Dose (200 mg/5 mL) | Total Course |
|---|---|---|---|
| 5 kg (11 lbs) | 1.25 mL (¼ tsp) | 0.625 mL | 150 mg |
| 10 kg (22 lbs) | 2.5 mL (½ tsp) | 1.25 mL (¼ tsp) | 300 mg |
| 20 kg (44 lbs) | 5 mL (1 tsp) | 2.5 mL (½ tsp) | 600 mg |
| 30 kg (66 lbs) | 7.5 mL (1½ tsp) | 3.75 mL (¾ tsp) | 900 mg |
| 40 kg (88 lbs) | 10 mL (2 tsp) | 5 mL (1 tsp) | 1200 mg |
| ≥50 kg (≥110 lbs) | 12.5 mL (2½ tsp) | 6.25 mL (1¼ tsp) | 1500 mg |
Intravenous Dosing
For hospitalized patients requiring IV therapy, administer 10 mg/kg IV once daily (maximum 500 mg) on days 1-2, then transition to oral therapy as soon as clinically feasible. 1
- IV azithromycin should be limited to the first 1-2 days only 1, 2
- Prolonged IV therapy beyond 2 days when oral therapy is feasible is inappropriate 1
- IV azithromycin is specifically indicated for atypical pathogens; typical bacterial pneumonia requires beta-lactam antibiotics as first-line therapy 1, 2
Critical Safety Considerations
Drug Interactions
- Do not administer simultaneously with aluminum- or magnesium-containing antacids, as they significantly reduce azithromycin absorption 1, 2
- Monitor for QT prolongation when used with other QT-prolonging medications 1, 2
Age-Specific Safety
- For infants <1 month receiving azithromycin for pertussis, monitor for infantile hypertrophic pyloric stenosis (IHPS), though azithromycin has not been definitively associated with IHPS 1
- The risk-benefit ratio favors treatment in young infants with pertussis exposure, as severe pertussis complications outweigh potential medication risks 1
Adverse Effects
- Gastrointestinal side effects (abdominal discomfort, diarrhea, nausea, vomiting) are the most common adverse events, occurring in approximately 9% of pediatric patients 6
- Azithromycin has fewer gastrointestinal side effects than erythromycin 1, 7
- Higher doses (20 mg/kg/day or 30 mg/kg single dose) are associated with more adverse effects but remain generally well-tolerated 5, 6
Common Pitfalls to Avoid
- Do not use azithromycin as first-line for typical bacterial pneumonia—beta-lactams (amoxicillin, amoxicillin-clavulanate) remain first-line for S. pneumoniae and H. influenzae 3, 2
- Do not underdose streptococcal pharyngitis—use 12 mg/kg/day for 5 days, not the standard 10 mg/kg regimen 2, 4
- Do not continue IV therapy beyond 2 days when oral therapy is feasible 1, 2
- Ensure the full 10 mg/kg dose is given to prevent underdosing and treatment failure 1