What is the recommended dose of azithromycin (Zithromax) for the treatment of community-acquired pneumonia?

Azithromycin Dosing for Community-Acquired Pneumonia

For adults with community-acquired pneumonia, the recommended dose of azithromycin is 500 mg on the first day, followed by 250 mg once daily for days 2 through 5, for a total treatment duration of 5 days. 1, 2

Adult Dosing Regimens

Standard 5-Day Regimen

• Day 1: 500 mg as a single dose
• Days 2-5: 250 mg once daily
• Total dose: 1.5 g

Alternative 3-Day Regimen

• 500 mg once daily for 3 days (total dose 1.5 g)
• This regimen is specifically mentioned by the European Respiratory Society as an acceptable alternative 2

Pediatric Dosing for Community-Acquired Pneumonia

For children 6 months and older:

• Day 1: 10 mg/kg as a single dose
• Days 2-5: 5 mg/kg once daily 1, 2

Important Considerations

Efficacy Factors

• Azithromycin should only be used as first-line monotherapy in areas where pneumococcal resistance is <25% (conditional recommendation, moderate quality evidence) 2
• For patients with comorbidities, combination therapy with a beta-lactam plus azithromycin is preferred over azithromycin monotherapy 2

Treatment Duration

• The minimum duration of treatment for most patients is 5 days (strong recommendation, moderate quality evidence) 2
• Treatment should be extended to 7-14 days for Legionella infections 2

Assessment of Response

• Assess response at 48-72 hours after initiating therapy 2
• Clinical improvement typically includes reduction in fever, improvement in respiratory symptoms, and stabilization of vital signs
• If no improvement after 48-72 hours, reassess diagnosis and consider alternative antimicrobial therapy 2

Special Populations

• No dosage adjustment is recommended for patients with renal impairment (GFR ≤80 mL/min) 1
• Caution should be exercised when azithromycin is administered to patients with severe renal impairment (GFR <10 mL/min) 1
• No dose adjustment recommendations can be made for patients with hepatic impairment 1

Clinical Pearls

• Azithromycin can be taken with or without food 1
• For severe pneumonia, the preferred regimen is a β-lactam (ceftriaxone, cefotaxime, ampicillin-sulbactam) plus a macrolide like azithromycin 2
• Patients should be afebrile for 48-72 hours and have no more than one CAP-associated sign of clinical instability before discontinuing therapy 2
• Patients with recent antibiotic exposure should receive treatment with antibiotics from a different class due to increased risk of bacterial resistance 2

While some studies have shown efficacy of single-dose (1.5 g) azithromycin for atypical pneumonia 3, the FDA-approved regimen and current guidelines recommend the 5-day course for community-acquired pneumonia to ensure adequate coverage of common pathogens.