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

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 for days 2-5, which is the standard 5-day regimen recommended by major guidelines. 1

Standard Dosing by Indication

Community-Acquired Pneumonia (Atypical Pathogens)

• The preferred regimen is 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 pneumonia caused by Mycoplasma pneumoniae, Chlamydia pneumoniae, or Chlamydia trachomatis 1, 2
• This 5-day regimen is endorsed by both the Infectious Diseases Society of America and the American Academy of Pediatrics 1
• Important 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

Acute Otitis Media

The FDA label provides three acceptable regimens 2:

• 30 mg/kg as a single dose (one-time treatment)
• 10 mg/kg once daily for 3 days
• 10 mg/kg on day 1, then 5 mg/kg daily for days 2-5 (standard 5-day regimen)

Acute Bacterial Sinusitis

• 10 mg/kg once daily for 3 days is the recommended regimen 2

Streptococcal Pharyngitis/Tonsillitis

• Azithromycin is second-line therapy only—penicillin or amoxicillin remain first-line 1
• When azithromycin must be used (e.g., penicillin allergy), a higher dose of 12 mg/kg once daily for 5 days (maximum 500 mg/day) is necessary due to high recurrence rates with the standard 10 mg/kg regimen 1, 2
• Studies show inferior bacteriologic eradication with 10 mg/kg for 3 days compared to penicillin, though clinical outcomes were similar 3

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 preferred over erythromycin in young infants due to better safety profile and no association with infantile hypertrophic pyloric stenosis (IHPS) 1

Mycobacterium Avium Complex (MAC) Prophylaxis

• 20 mg/kg (maximum 1,200 mg) once weekly for HIV-infected children 1

Genital Chlamydial Infections (Adolescents)

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

Weight-Based Dosing Table

For children on the standard 5-day regimen, the Thorax guideline society provides specific weight-based dosing 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 Azithromycin

When parenteral therapy is required for atypical pneumonia, administer 10 mg/kg IV once daily (maximum 500 mg) on days 1 and 2, then transition to oral therapy as soon as clinically feasible 1

Key considerations:

• IV therapy should be limited to days 1-2 only when oral therapy is feasible 1
• IV azithromycin is specifically indicated for atypical pathogens; typical bacterial pneumonia requires beta-lactam antibiotics as first-line 1

Alternative Macrolides for Allergic Patients

If azithromycin cannot be used 1, 4:

• Clarithromycin: 15 mg/kg/day divided into 2 doses (preferred due to better tolerability and twice-daily dosing)
• Erythromycin: 40 mg/kg/day divided into 4 doses
• Doxycycline: Only for children >7 years old due to dental staining concerns

Critical Safety Considerations

Drug Interactions

• Avoid concurrent administration with aluminum- or magnesium-containing antacids, as they reduce absorption 1
• Monitor for QT interval prolongation when used with other QT-prolonging medications 1
• Exercise caution with drugs metabolized by cytochrome P450 enzyme system 1

Adverse Effects

• Common side effects include abdominal discomfort, diarrhea, nausea, vomiting, headache, and dizziness 1
• Azithromycin has fewer gastrointestinal side effects compared to erythromycin 1, 5
• Studies show significantly lower rates of diarrhea with azithromycin (5 cases) versus co-amoxiclav (32 cases) 5

Special Populations

• Severe renal impairment (GFR <10 mL/min): Use with caution, as AUC increases 35% 2
• Hepatic impairment: No dose adjustment recommendations available due to lack of pharmacokinetic data 2
• Infants <1 month: Azithromycin is preferred for pertussis despite limited data, as benefits outweigh risks 1

Common Pitfalls to Avoid

• Never exceed adult maximum doses regardless of weight: 500 mg on day 1 and 250 mg daily for the 5-day respiratory regimen 1
• Do not use the standard 10 mg/kg dose for strep throat—this leads to high recurrence rates; use 12 mg/kg for 5 days instead 1
• Do not use azithromycin as first-line for typical bacterial pneumonia or strep throat—it is second-line only 1
• Avoid prolonged IV therapy beyond 2 days when oral therapy is feasible 1
• Azithromycin can be taken with or without food 2