What is the recommended dosage of azithromycin (macrolide antibiotic) for pediatric patients?

Azithromycin Pediatric Dosing

For most pediatric infections, administer azithromycin 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 for children ≥6 months with atypical pneumonia caused by Mycoplasma pneumoniae, Chlamydia pneumoniae, or Chlamydia trachomatis 1, 2
• This 5-day regimen is recommended by both the American Academy of Pediatrics and the Infectious Diseases Society of America 1, 3
• 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 1, 2

Acute Otitis Media

• Three FDA-approved 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 day 1, then 5 mg/kg daily days 2-5 (5-day regimen)
• All three regimens demonstrated equivalent efficacy to amoxicillin/clavulanic acid in clinical trials 5, 6

Acute Bacterial Sinusitis

• 10 mg/kg once daily for 3 days for children ≥6 months 1, 4

Streptococcal Pharyngitis/Tonsillitis

• 12 mg/kg once daily for 5 days (maximum 500 mg/day) 1
• Important: Azithromycin is second-line therapy only—penicillin or amoxicillin remains first-line 1, 2
• The higher dose (12 mg/kg vs. standard 10 mg/kg) is necessary because the standard regimen results in high recurrence rates 1
• Studies show inferior bacteriologic eradication (65% vs. 82% with penicillin) despite similar clinical success rates 7

Pertussis Treatment and Prophylaxis

• Infants <6 months: 10 mg/kg once daily for 5 days 1, 2
• Children ≥6 months: 10 mg/kg (max 500 mg) day 1, then 5 mg/kg (max 250 mg) daily days 2-5 1
• Azithromycin is the preferred macrolide for infants <1 month due to better safety profile compared to erythromycin 1, 3

Weight-Based Dosing Table

For children requiring weight-based dosing (when standard mg/kg calculation is impractical) 1:

• 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

Intravenous Administration

Limit IV azithromycin to days 1-2 only, then transition to oral therapy when clinically feasible 1, 2:

• 10 mg/kg IV once daily (maximum 500 mg) on days 1 and 2 1
• Administer at 1 mg/mL concentration over 3 hours OR 2 mg/mL concentration over 1 hour 1
• IV azithromycin is specifically indicated for atypical pathogens requiring parenteral therapy 1

Administration Guidelines

Timing and Food

• Azithromycin can be taken with or without food 4
• Do NOT administer simultaneously with aluminum- or magnesium-containing antacids—separate by at least 2 hours, as antacids reduce absorption 1, 2, 3

Formulation

• Oral suspension is the preferred formulation for children who cannot swallow tablets 1
• Reconstitute suspension with water before administration 1

Critical Safety Considerations

Drug Interactions

• Monitor for QT prolongation when used with other QT-prolonging medications 2, 3
• Exercise caution with drugs metabolized by cytochrome P450 enzyme system 1

Adverse Effects

• Common gastrointestinal effects include abdominal discomfort, diarrhea, nausea, and vomiting 1, 3
• Azithromycin has fewer GI side effects than erythromycin 1, 2
• Overall adverse event rate in pediatric studies: 8.7% (mostly mild-moderate severity) 6
• Treatment discontinuation due to adverse events: only 1.3% 6

Special Populations

• Infants <1 month: Azithromycin is safe and preferred for pertussis; not associated with infantile hypertrophic pyloric stenosis (IHPS), though monitoring is recommended 1
• Severe renal impairment (GFR <10 mL/min): Use with caution—AUC increases 35% 4
• Hepatic impairment: Biliary excretion is the main route of elimination; use caution 1

Common Pitfalls to Avoid

1. Do not use azithromycin as first-line for typical bacterial pneumonia—beta-lactams remain first-line for S. pneumoniae and H. influenzae 1, 2
2. Do not use the standard 10 mg/kg regimen for strep throat—requires 12 mg/kg daily for 5 days due to high recurrence rates 1
3. Do not prolong IV therapy beyond 2 days when oral therapy is feasible 1, 2
4. Do not exceed adult maximum doses regardless of weight (500 mg day 1,250 mg days 2-5) 1

Expected Clinical Response

Children on adequate azithromycin therapy should demonstrate clinical improvement within 48-72 hours 1. If the patient deteriorates or shows no improvement within this timeframe, further investigation is warranted, including assessment for complications such as parapneumonic effusion 1.