Azithromycin Dosing for an 11-Year-Old with Community-Acquired Pneumonia
For an 11-year-old patient weighing 47 kg with community-acquired pneumonia, azithromycin should be dosed at 10 mg/kg (470 mg, rounded to 500 mg) on day 1, followed by 5 mg/kg/day (235 mg, rounded to 250 mg) once daily on days 2 through 5, for a total 5-day course. 1, 2
Dosing Calculation and Administration
The standard pediatric dosing regimen for CAP is 10 mg/kg as a single dose on day 1, followed by 5 mg/kg once daily for days 2-5 1, 2
For this 47 kg patient:
- Day 1: 470 mg (round to 500 mg)
- Days 2-5: 235 mg (round to 250 mg daily) 2
This can be administered using azithromycin oral suspension (200 mg/5 mL): 12.5 mL on day 1, then 6.25 mL daily on days 2-5 2
Alternatively, tablets can be used: 500 mg tablet on day 1, then 250 mg tablet daily on days 2-5 2
Azithromycin can be taken with or without food 2
Clinical Context and Rationale
Azithromycin is specifically indicated when atypical pathogens (Mycoplasma pneumoniae or Chlamydophila pneumoniae) are significant considerations in hospitalized or outpatient children with CAP 3, 1
For children ≥5 years old, atypical pathogens become increasingly common causes of CAP, making macrolide coverage appropriate 1
The Infectious Diseases Society of America recommends empiric combination therapy with a macrolide in addition to a β-lactam antibiotic for hospitalized children when atypical pathogens are suspected 3
If this patient is being treated as an outpatient with presumed atypical pneumonia, azithromycin monotherapy is appropriate 1
Important Clinical Considerations
Children should demonstrate clinical improvement within 48-72 hours of starting appropriate therapy 1, 4
If no improvement occurs within this timeframe, reevaluation is necessary and consideration should be given to alternative pathogens or complications 1, 4
The 5-day azithromycin regimen has been shown to be as effective as 7-10 day courses of other antibiotics for pediatric CAP, with significantly fewer side effects 5
Microbiologic eradication rates for M. pneumoniae are 100% with azithromycin in pediatric studies 5
Common Pitfalls to Avoid
Do not use the adult 3-day regimen (500 mg daily × 3 days) in pediatric patients—the 5-day weight-based regimen is the FDA-approved pediatric dosing 2
Do not use the single 30 mg/kg dose regimen for CAP—this is only approved for acute otitis media, not pneumonia 2
Avoid using azithromycin monotherapy if typical bacterial pathogens (particularly Streptococcus pneumoniae) are strongly suspected—in such cases, high-dose amoxicillin (90 mg/kg/day) is preferred 1
For hospitalized patients requiring parenteral therapy, intravenous azithromycin is dosed at 10 mg/kg on days 1 and 2, then transition to oral therapy when appropriate 1, 6