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

Azithromycin Dosing for Adolescents

For adolescents, azithromycin is 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 for most respiratory infections, or a single 1 gram dose for uncomplicated genital chlamydial infections. 1

Standard Dosing by Indication

Respiratory Tract Infections (Community-Acquired Pneumonia, Atypical Pneumonia)

• The preferred regimen is 10 mg/kg (maximum 500 mg) on day 1, then 5 mg/kg (maximum 250 mg) once daily for days 2-5 2, 3, 1
• This 5-day course is specifically recommended for atypical pathogens including Mycoplasma pneumoniae, Chlamydia pneumoniae, and Chlamydia trachomatis 2, 4
• For adolescents weighing ≥50 kg (≥110 lbs), the adult dose applies: 500 mg on day 1, then 250 mg daily for days 2-5 1

Pharyngitis/Tonsillitis (Second-Line Therapy)

• A higher dose of 12 mg/kg once daily for 5 days (maximum 500 mg/day) is required due to higher recurrence rates with standard dosing 3, 1, 5
• This indication requires azithromycin to be used as second-line therapy only, with penicillin or amoxicillin remaining first-line 3

Genital Chlamydial Infections

• A single 1 gram oral dose is the recommended treatment for uncomplicated urethritis or cervicitis caused by Chlamydia trachomatis 2, 1, 6
• This single-dose regimen has been shown to be as effective as 7 days of doxycycline in adolescents, with the significant advantage of ensuring compliance 6

Acute Bacterial Sinusitis

• The recommended dose is 10 mg/kg once daily for 3 days (maximum 500 mg/day) 1

Weight-Based Dosing for Adolescents

For adolescents who weigh less than adult weight thresholds, use these weight-based guidelines 3:

• 26-35 kg: 300 mg once daily
• 36-45 kg: 400 mg once daily
• ≥46 kg: 500 mg once daily (adult dose)

Intravenous Therapy

When parenteral therapy is required for severe 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 2, 3
• Prolonged IV therapy beyond 2 days should be avoided when oral therapy is tolerated 3

Important Clinical Considerations

Common Pitfalls to Avoid

• Do not use the standard 10 mg/kg dosing for streptococcal pharyngitis—this leads to high recurrence rates; the 12 mg/kg dose is necessary 3, 5
• Azithromycin is not first-line for typical bacterial pneumonia caused by S. pneumoniae or H. influenzae; amoxicillin remains preferred for these pathogens 3
• Avoid concurrent administration with aluminum- or magnesium-containing antacids, as they reduce absorption 3

Tolerability Profile

• Azithromycin is generally well-tolerated in adolescents, with approximately 9-19% experiencing mild to moderate gastrointestinal side effects (abdominal discomfort, diarrhea, nausea) 3, 5, 7
• The adverse effect profile is equal or superior to comparator antibiotics, with only 0.7% of patients discontinuing therapy 8
• Side effects rarely necessitate treatment withdrawal 7

Drug Interactions

• Monitor for QT interval prolongation when used with other medications that affect cardiac conduction 3
• Exercise caution with drugs metabolized by the cytochrome P450 enzyme system 3

Maximum Doses

• Oral doses should never exceed adult doses regardless of weight 2
• For the 5-day respiratory regimen: maximum 500 mg on day 1, then 250 mg daily 1
• For pharyngitis: maximum 500 mg daily for 5 days 1