What is the recommended oral azithromycin dosing in children (weight‑based) for common infections and special indications?

Azithromycin Dosing for Pediatric Patients

For most common pediatric infections, give azithromycin 10 mg/kg (maximum 500 mg) on day 1, then 5 mg/kg (maximum 250 mg) once daily on days 2–5. This 5-day regimen is the standard recommendation from the Infectious Diseases Society of America, the American Academy of Pediatrics, and the CDC for community-acquired pneumonia and atypical respiratory infections in children ≥6 months 1, 2, 3.

Standard Weight-Based Dosing by Indication

Community-Acquired Pneumonia & Atypical Respiratory Infections (≥6 months)

• Day 1: 10 mg/kg once (maximum 500 mg) 1, 2, 3
• Days 2–5: 5 mg/kg once daily (maximum 250 mg) 1, 2, 3
• This regimen achieves therapeutic tissue concentrations for Mycoplasma pneumoniae, Chlamydia pneumoniae, and Chlamydia trachomatis 1, 2
• Do not use azithromycin as first-line for typical bacterial pneumonia caused by Streptococcus pneumoniae or Haemophilus influenzae; amoxicillin 90 mg/kg/day remains preferred 1, 2

Acute Otitis Media (≥6 months)

• Option 1 (5-day): 10 mg/kg day 1, then 5 mg/kg days 2–5 3
• Option 2 (3-day): 10 mg/kg once daily for 3 days 3
• Option 3 (1-day): 30 mg/kg as a single dose 3
• The FDA label supports all three regimens; the 5-day course is most commonly used 3

Acute Bacterial Sinusitis (≥6 months)

• 10 mg/kg once daily for 3 days 3

Streptococcal Pharyngitis (≥2 years, second-line only)

• 12 mg/kg once daily for 5 days (maximum 500 mg/day) 1, 2, 3
• Penicillin or amoxicillin remain first-line; azithromycin requires this higher dose to reduce recurrence rates 1, 2

Pertussis Treatment & Prophylaxis

• Infants <6 months: 10 mg/kg once daily for 5 days 1
• Children ≥6 months: 10 mg/kg (max 500 mg) day 1, then 5 mg/kg (max 250 mg) days 2–5 1
• Azithromycin is preferred over erythromycin in neonates due to lower risk of infantile hypertrophic pyloric stenosis 1

MAC Prophylaxis in HIV-Infected Children

• 20 mg/kg once weekly (maximum 1,200 mg per dose) 1, 2

Simplified Weight-Band Dosing (British Thoracic Society)

For once-daily regimens, the following weight bands simplify dosing 1, 2:

Weight (kg)	Daily Dose
15–25 kg	200 mg
26–35 kg	300 mg
36–45 kg	400 mg
≥46 kg	500 mg

Intravenous Dosing (Hospitalized Patients)

• 10 mg/kg IV once daily (maximum 500 mg) on days 1–2, then transition to oral therapy as soon as feasible 1, 2
• Infuse at 1 mg/mL over 3 hours OR 2 mg/mL over 1 hour 1
• IV azithromycin is specifically indicated for atypical pathogens when parenteral therapy is required 1

Critical Administration Considerations

• Separate from antacids: Do not give azithromycin simultaneously with aluminum- or magnesium-containing antacids; separate by at least 2 hours to avoid 30% reduction in absorption 1, 2
• Food: Azithromycin can be taken with or without meals 2, 3
• Oral suspension: Must be reconstituted with water before administration 2

Expected Clinical Response & When to Reassess

• Children should show clinical improvement within 48–72 hours of starting azithromycin 1, 2
• If no improvement or deterioration occurs within this window, reassess for:
  • Incorrect diagnosis or resistant pathogens 2
  • Complications such as parapneumonic effusion 1
  • Need for alternative antimicrobial therapy 1, 2

Common Pitfalls to Avoid

• Do not underdose day 1: The full 10 mg/kg loading dose is essential to achieve therapeutic tissue levels 1, 2
• Do not use for typical bacterial pneumonia: Azithromycin is inferior to amoxicillin for S. pneumoniae and H. influenzae 1, 2
• Do not use as first-line for strep throat: Penicillin/amoxicillin have superior outcomes; if azithromycin is necessary, use the higher 12 mg/kg dose 1, 2
• Do not split into twice-daily dosing: All guidelines uniformly recommend once-daily administration; there is no evidence supporting BID dosing in children 2

Safety Profile

• Common adverse effects: Diarrhea (5–6%), vomiting (2–6%), abdominal discomfort, nausea 1, 2
• Better tolerated than alternatives: Azithromycin causes significantly fewer GI events than erythromycin (2% vs 29% diarrhea) and is better tolerated than amoxicillin/clavulanate 1, 2
• Discontinuation rate: Approximately 1% of pediatric courses 2

Monitoring Requirements

• Short courses (3–5 days): No routine laboratory or cardiac monitoring required 2
• Prolonged therapy (e.g., NTM infection): Obtain baseline ECG, repeat at 2 weeks and after adding QT-prolonging drugs; perform baseline and intermittent audiometry; check liver/renal function and CBC intermittently 1, 2

Special Populations

Neonates (<1 month)

• 10 mg/kg once daily for 5 days for pertussis treatment/prophylaxis 1
• CDC states the benefit of treating pertussis outweighs the potential risk of IHPS 1
• Monitor for IHPS signs (projectile vomiting, visible peristaltic waves) 1
• Azithromycin has not been associated with IHPS, unlike erythromycin 1

Adolescents with Chlamydial Infections

• Single 1-gram oral dose for uncomplicated urethritis or cervicitis caused by Chlamydia trachomatis 1