What are the appropriate antibiotic therapies and durations for outpatient community-acquired pneumonia?

Outpatient Community-Acquired Pneumonia Treatment

For healthy adults without comorbidities, amoxicillin 1 gram three times daily for 5-7 days is the first-line treatment, with doxycycline 100 mg twice daily for 5-7 days as the preferred alternative. 1, 2, 3

Treatment Algorithm by Patient Risk Category

Healthy Adults WITHOUT Comorbidities

First-line options (choose one):

• Amoxicillin 1 g three times daily (strong recommendation, moderate quality evidence) 1, 2

  • Duration: 5-7 days 2, 3
  • Most effective against Streptococcus pneumoniae, the most common pathogen 2

• Doxycycline 100 mg twice daily (conditional recommendation, low quality evidence) 1, 2

  • Duration: 5-7 days 2, 3
  • Provides broader coverage including atypical organisms 2

• Azithromycin 500 mg day 1, then 250 mg daily (conditional recommendation) 1, 2

  • Duration: 5 days total 2, 3
  • ONLY use if local pneumococcal macrolide resistance is documented <25% 1, 2
  • Do NOT use with recent antibiotic exposure or any comorbidities 2, 3

Adults WITH Comorbidities

(chronic heart/lung/liver/renal disease, diabetes, alcoholism, malignancy, asplenia)

Combination therapy (preferred):

• Amoxicillin/clavulanate 875 mg/125 mg twice daily PLUS azithromycin (500 mg day 1, then 250 mg daily) 1, 2

  • Duration: 5-7 days 2, 3
  • Strong recommendation, moderate quality evidence 1

• Amoxicillin/clavulanate 2,000 mg/125 mg twice daily PLUS doxycycline 100 mg twice daily 1, 3

  • Duration: 5-7 days 2, 3

Monotherapy alternative:

• Levofloxacin 750 mg once daily 1, 4

  • Duration: 5 days 4
  • Strong recommendation, moderate quality evidence 1
  • Active against >98% of S. pneumoniae strains including resistant isolates 2

• Moxifloxacin 400 mg once daily 1

  • Duration: 5-7 days 2

Duration Guidelines and Clinical Stability Criteria

Standard duration is 5-7 days when ALL clinical stability criteria are met: 2, 3

• Temperature ≤37.8°C 3
• Heart rate ≤100 beats/min 3
• Respiratory rate ≤24 breaths/min 3
• Systolic blood pressure ≥90 mmHg 3
• Oxygen saturation ≥90% on room air 3
• Ability to maintain oral intake 3
• Normal mental status 3

Extend to 14-21 days ONLY for: 2, 3

• Suspected or confirmed Legionella pneumophila 2, 3
• Staphylococcus aureus infection 2, 3
• Gram-negative enteric bacilli 2, 3

Critical Pitfalls to Avoid

Macrolide monotherapy should NEVER be used in: 2, 3

• Patients with any comorbidities 2, 3
• Areas where pneumococcal macrolide resistance ≥25% 1, 2
• Patients with recent antibiotic use (within 90 days) 2
• Patients requiring hospitalization 3

Fluoroquinolone cautions: 2

• Reserve for patients with comorbidities or when other options cannot be used 2
• Risk of tendinopathy, peripheral neuropathy, and CNS effects 2

Recent antibiotic exposure: 2

• Choose a different antibiotic class than used within the past 90 days to reduce resistance risk 2

Monitoring Response

Fever should resolve within 2-3 days after initiating treatment. 2, 3

• If no clinical improvement by day 2-3, reassess for alternative diagnoses, complications, or resistant pathogens rather than automatically extending duration 2, 3
• For outpatients, reassess at day 5-7 if symptoms persist 2