When to Use Azithromycin
Azithromycin should be used as a second-line agent for specific bacterial infections when first-line treatments have failed, are contraindicated, or when patient adherence to longer regimens is a concern. 1
Primary Indications for Azithromycin
Respiratory Tract Infections
- Acute bacterial exacerbations of COPD caused by Haemophilus influenzae, Moraxella catarrhalis, or Streptococcus pneumoniae 2
- Acute bacterial sinusitis due to H. influenzae, M. catarrhalis, or S. pneumoniae 2
- Community-acquired pneumonia in patients appropriate for oral therapy caused by:
- Chlamydophila pneumoniae
- Haemophilus influenzae
- Mycoplasma pneumoniae
- Streptococcus pneumoniae 2
Sexually Transmitted Infections
- Chlamydial infections: 1g orally as a single dose 1, 3
- Cervicitis due to Chlamydia trachomatis or Neisseria gonorrhoeae 3, 2
- Urethritis due to Chlamydia trachomatis or Neisseria gonorrhoeae 2
- Genital ulcer disease in men due to Haemophilus ducreyi (chancroid) 2
Skin and Soft Tissue Infections
- Uncomplicated skin and skin structure infections due to:
- Staphylococcus aureus (methicillin-susceptible)
- Streptococcus pyogenes
- Streptococcus agalactiae 2
Pediatric Indications
- Acute otitis media caused by H. influenzae, M. catarrhalis, or S. pneumoniae 2
- Pharyngitis/tonsillitis caused by S. pyogenes as an alternative to first-line therapy 2
- Note: Penicillin remains the drug of choice for streptococcal pharyngitis 2
Special Populations
Children
- <45kg: Erythromycin base or ethylsuccinate 50mg/kg/day divided into four doses for 14 days 1
- >45kg but <8 years: Azithromycin 1g orally, single dose 1
- ≥8 years: Azithromycin 1g orally single dose OR Doxycycline 100mg twice daily for 7 days 1
Pregnant Women
- Azithromycin 1g orally as a single dose is recommended for chlamydial infections, as doxycycline is contraindicated 3
Important Considerations and Cautions
Antimicrobial Resistance Concerns
- The efficacy of azithromycin against Mycoplasma genitalium has decreased significantly over time, with cure rates falling from 85.3% before 2009 to 67.0% since 2009 1
- Azithromycin's long half-life (68 hours) creates a prolonged period of subinhibitory concentrations, which may promote the development of resistant strains 1
- FDA has issued warnings about the safety of azithromycin, contributing to recommendations for its use as a second-line agent 1
Contraindications
- Pneumonia in high-risk patients: Not appropriate for patients with cystic fibrosis, nosocomial infections, known/suspected bacteremia, requiring hospitalization, or with significant underlying health problems 2
- Current NTM (non-tuberculous mycobacterial) infection: Azithromycin monotherapy is contraindicated due to risk of developing macrolide-resistant NTM disease, which has very poor treatment outcomes 1
Monitoring and Follow-up
- For STIs: Test of cure recommended for pregnant women, when using alternative regimens, or when there are concerns about adherence 3
- Rescreening recommended 3-6 months after treatment due to high risk of reinfection 3
Algorithm for Azithromycin Use Decision-Making
- Identify the infection type and likely pathogens
- Determine if first-line therapy is appropriate:
- For respiratory infections: Consider beta-lactams first
- For streptococcal pharyngitis: Penicillin is first-line
- For chlamydial infections: Doxycycline is first-line (unless contraindicated)
- Consider azithromycin if:
- First-line therapy has failed
- Patient has contraindications to first-line therapy
- Adherence to multi-day regimens is a concern
- Specific pathogens are likely (e.g., atypical respiratory pathogens)
- Screen for contraindications to azithromycin:
- History of NTM infection
- Severe pneumonia requiring hospitalization
- QT prolongation or risk factors
- Select appropriate dosing regimen based on infection type and patient characteristics
By following this evidence-based approach, azithromycin can be used effectively while minimizing the risk of contributing to antimicrobial resistance.