Azithromycin 500mg for Tonsillitis: 5-Day Course
For tonsillitis (streptococcal pharyngitis), azithromycin 500mg should be taken once daily for 5 days total: 500mg on day 1, followed by 250mg once daily on days 2 through 5. 1
Standard Dosing Regimen
The Infectious Diseases Society of America (IDSA) guidelines specifically recommend for Group A Streptococcal pharyngitis (which includes tonsillitis):
- 12 mg/kg once daily (maximum 500mg) for 5 days 1
- This translates to 500mg on day 1, then 250mg daily for days 2-5 in most adults 2
The FDA-approved labeling confirms this exact regimen for pharyngitis/tonsillitis: 500mg as a single dose on Day 1, followed by 250mg once daily on Days 2 through 5 2
Critical Clinical Considerations
Azithromycin is NOT first-line therapy for streptococcal tonsillitis. 1 The IDSA guidelines classify azithromycin as having "strong, moderate" evidence strength, whereas penicillin and amoxicillin have "strong, high" evidence ratings 1
When to Use Azithromycin:
- Penicillin allergy is the primary indication for using azithromycin instead of first-line agents 1
- Avoid in patients with immediate-type hypersensitivity to penicillin who can tolerate cephalosporins, as cephalexin or cefadroxil are preferred alternatives 1
Important Resistance Warning:
The IDSA guidelines explicitly note that "resistance of GAS to these agents is well-known and varies geographically and temporally" 1. This means azithromycin may be less effective in areas with high macrolide resistance rates.
Why Not 3 Days?
While a 3-day regimen (500mg daily for 3 days) is FDA-approved for other respiratory infections like sinusitis and bronchitis 2, the 5-day regimen is specifically required for streptococcal pharyngitis/tonsillitis 1, 2. Clinical studies demonstrated that the shorter 12 mg/kg/day for 5 days dosing was necessary to achieve adequate bacteriologic eradication rates comparable to 10 days of penicillin 2, 3
Administration Details
- Can be taken with or without food 2
- Separate from antacids by at least 2 hours - aluminum or magnesium-containing antacids reduce absorption by up to 50% 4
- Directly observe the first dose when possible to maximize adherence 5
Treatment Goals
Appropriate antibiotic therapy for streptococcal tonsillitis is critical for:
- Prevention of acute rheumatic fever 1
- Prevention of suppurative complications (peritonsillar abscess, cervical lymphadenitis) 1
- Symptom relief and shortened contagious period 1
- Reduction of transmission to close contacts 1
Common Pitfalls
Do not use the single 1-gram dose regimen - this is only appropriate for chlamydial infections, not streptococcal pharyngitis 2, 6. The 5-day course is required to maintain tissue concentrations above the MIC for Streptococcus pyogenes for the full treatment duration 6