What is the dosage and treatment duration of Azithromycin for various bacterial infections?

Azithromycin Dosing and Treatment Duration

For most bacterial infections, azithromycin should be dosed as 500 mg on day 1 followed by 250 mg daily on days 2-5, or alternatively 500 mg daily for 3 days, with treatment duration typically limited to 3-7 days depending on the specific infection. 1, 2

Adult Dosing by Indication

Respiratory Tract Infections

• Community-acquired pneumonia (mild): 500 mg on day 1, then 250 mg daily on days 2-5 (total 5 days) 2
• Acute bacterial exacerbations of COPD: Either 500 mg daily for 3 days OR 500 mg on day 1 followed by 250 mg daily on days 2-5 2
• Acute bacterial sinusitis: 500 mg daily for 3 days 2
• Pharyngitis/tonsillitis (second-line only): 500 mg on day 1, then 250 mg daily on days 2-5 2

Severe or Hospitalized Pneumonia

• Legionnaires' disease (hospitalized): 500 mg IV daily for 2-7 days, then transition to oral to complete 7-10 days total 3
• Legionnaires' disease (non-hospitalized): 500 mg on day 1, then 250 mg daily for 4 additional days 3
• Community-acquired pneumonia requiring hospitalization: Total duration 7-10 days 4

Sexually Transmitted Infections

• Non-gonococcal urethritis/cervicitis (Chlamydia): Single 1-gram dose 2
• Gonococcal urethritis/cervicitis: Single 2-gram dose 2
• Genital ulcer disease (chancroid): Single 1-gram dose 2

Gastrointestinal Infections

• Travelers' diarrhea with dysentery: Single 1-gram dose OR 500 mg daily for 3 days 1

Skin and Soft Tissue Infections

• Uncomplicated skin/skin structure infections: 500 mg on day 1, then 250 mg daily on days 2-5 2

Pediatric Dosing (Age ≥6 months)

Standard Regimens

• Acute otitis media: Three options available 2:

  • Single 30 mg/kg dose (1-day regimen)
  • 10 mg/kg daily for 3 days (3-day regimen)
  • 10 mg/kg on day 1, then 5 mg/kg daily on days 2-5 (5-day regimen)

• Community-acquired pneumonia: 10 mg/kg on day 1, then 5 mg/kg daily on days 2-5 (5-day regimen only) 2

• Acute bacterial sinusitis: 10 mg/kg daily for 3 days (3-day regimen only) 2

• Pharyngitis/tonsillitis (age ≥2 years): 12 mg/kg daily for 5 days 2

Atypical Pathogens in Children

• Mycoplasma pneumoniae, Chlamydia trachomatis, or Chlamydophila pneumoniae: 10 mg/kg on day 1, then 5 mg/kg daily on days 2-5 3

Critical Safety Considerations

Cardiac Monitoring Required

• Obtain baseline ECG before initiating therapy in patients with cardiac risk factors 1, 3
• Avoid azithromycin if QTc >450 ms (men) or >470 ms (women) 1, 3
• Azithromycin can cause fatal cardiac arrhythmias including torsades de pointes, particularly in patients with known QT prolongation 4

Resistance and Stewardship Concerns

• Azithromycin's 68-hour half-life creates a 14-20 day "window" of subinhibitory drug concentrations that may promote resistance development 5, 4
• High macrolide resistance rates in many regions favor alternative agents as first-line therapy 4
• Not recommended as first-line for streptococcal pharyngitis; use only in penicillin-allergic patients 3
• Doxycycline is preferred for chlamydial urethritis; use azithromycin only if doxycycline fails, is contraindicated, or adherence is a concern 4

Tuberculosis Screening

• Empiric azithromycin for pneumonia may delay tuberculosis diagnosis; consider TB screening in high-risk populations before initiating therapy 4

Special Populations

Renal Impairment

• No dosage adjustment needed for GFR 10-80 mL/min 2
• Exercise caution in severe renal impairment (GFR <10 mL/min) as AUC increases by 35% 2

Hepatic Impairment

• No established dosing recommendations; pharmacokinetics have not been studied in hepatic impairment 2

Common Pitfalls to Avoid

• Do not use azithromycin as first-line for strep pharyngitis due to higher recurrence rates compared to penicillin 6
• Amoxicillin-clavulanate shows superior efficacy compared to macrolides in head-to-head trials for acute bacterial sinusitis 4
• Beta-lactams remain first-line for hospitalized patients with community-acquired pneumonia 4
• Gastrointestinal adverse effects (nausea, vomiting, diarrhea) occur in approximately 3% of patients 1
• Avoid administering with large meals as absorption may be reduced by up to 50% 7

Administration

• Can be taken with or without food for both tablets and oral suspension 2
• If pediatric patient vomits within 30 minutes of 30 mg/kg single dose, re-dosing at the same total dose has been studied in limited cases 2