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

Azithromycin Dosing for Outpatient Community-Acquired Pneumonia

For adults with outpatient community-acquired pneumonia (CAP), the recommended dose of azithromycin is 500 mg on day 1, followed by 250 mg once daily for days 2 through 5. 1, 2

Adult Dosing

Standard Adult Regimen

• 500 mg as a single dose on Day 1
• 250 mg once daily on Days 2-5
• Total treatment duration: 5 days
• Can be taken with or without food 1

This dosing regimen is recommended by both the FDA and clinical guidelines as first-line treatment for adults with mild CAP without comorbidities 2, 1.

Special Populations

Patients with Comorbidities

• For patients with chronic heart, lung, liver, or renal disease; diabetes mellitus; alcoholism; malignancy; or asplenia:
  • Consider combination therapy with a beta-lactam (amoxicillin/clavulanate, cefpodoxime, or cefuroxime) plus azithromycin at standard doses 2

Renal Impairment

• No dosage adjustment needed for GFR 10-80 mL/min
• Use caution in severe renal impairment (GFR <10 mL/min) as AUC increases by 35% 1, 2

Hepatic Impairment

• No specific dosage recommendations available for hepatic impairment 1

Pediatric Dosing for CAP

• For children ≥6 months:
  • 10 mg/kg on day 1, followed by 5 mg/kg daily for days 2-5 2, 1
  • Weight-based dosing examples are provided in the FDA label 1

Important Clinical Considerations

Antibiotic Resistance

• Macrolides should only be used as monotherapy in areas where pneumococcal resistance to macrolides is <25% 2
• Patients with recent antibiotic exposure should receive treatment with antibiotics from a different class 2

Drug Interactions

• Be cautious when using azithromycin in patients taking other medications that prolong the QT interval 2

Treatment Assessment

• Assess for clinical improvement within 48-72 hours of starting therapy 2
• Clinical improvement includes:
  • Reduction in fever
  • Improvement in respiratory symptoms
  • Stabilization of vital signs 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

Common Pitfalls to Avoid

1. Using macrolide monotherapy in areas with high pneumococcal resistance
2. Failing to consider combination therapy for patients with comorbidities
3. Not monitoring for clinical improvement within 48-72 hours
4. Overlooking potential QT interval prolongation with concomitant medications

The evidence strongly supports the 5-day azithromycin regimen (500 mg day 1,250 mg days 2-5) as effective therapy for outpatient CAP, with both FDA labeling and clinical guidelines aligned on this recommendation.