What is the recommended outpatient treatment for a adult patient with mild to moderate community-acquired pneumonia (CAP) and no significant underlying health conditions?

Outpatient Treatment of Community-Acquired Pneumonia

For previously healthy adults with mild to moderate community-acquired pneumonia and no significant comorbidities, amoxicillin 1 gram orally three times daily for 5-7 days is the first-line treatment, with doxycycline 100 mg twice daily as the preferred alternative. 1, 2, 3

Treatment Algorithm for Healthy Adults Without Comorbidities

First-line therapy:

• Amoxicillin 1 g orally three times daily for 5-7 days provides excellent coverage against Streptococcus pneumoniae, the most common pathogen in CAP, with activity against 90-95% of pneumococcal strains including many penicillin-resistant isolates 1, 2, 3
• This regimen has strong recommendation with moderate-quality evidence from the American Thoracic Society and Infectious Diseases Society of America 1, 2

Alternative therapy:

• Doxycycline 100 mg orally twice daily for 5-7 days serves as an acceptable alternative, providing broad-spectrum coverage including atypical organisms 1, 2, 3
• Consider a 200 mg loading dose on day 1 3
• This carries a conditional recommendation with lower quality evidence 1, 2

Macrolide monotherapy (azithromycin or clarithromycin):

• Should only be used when local pneumococcal macrolide resistance is documented to be <25% 1, 2, 3
• Azithromycin dosing: 500 mg on day 1, then 250 mg daily on days 2-5 4
• Macrolide monotherapy should be avoided in areas with ≥25% resistance due to risk of treatment failure and breakthrough pneumococcal bacteremia 1, 2

Critical Decision Points to Prevent Treatment Failure

Recent antibiotic exposure:

• If the patient used antibiotics within the past 90 days, select an agent from a different antibiotic class to reduce resistance risk 1, 3
• This is a strong recommendation to prevent selection of resistant organisms 1

Avoid fluoroquinolones as first-line:

• Respiratory fluoroquinolones (levofloxacin, moxifloxacin) should be reserved for patients with comorbidities or when other options cannot be used 1, 3
• The FDA has issued warnings about serious adverse effects including tendinopathy, peripheral neuropathy, and CNS effects 1
• Avoid in patients with cardiac arrhythmias, vascular disease, or history of Clostridium difficile infection 3

Treatment Duration and Monitoring

Standard duration:

• Treat for a minimum of 5 days and until the patient is afebrile for 48-72 hours with no more than one sign of clinical instability 1, 2, 3
• Typical duration for uncomplicated CAP is 5-7 days 1, 2, 3

Extended duration (14-21 days) required only for:

• Legionella pneumophila (suspected or confirmed) 1, 3
• Staphylococcus aureus 1, 3
• Gram-negative enteric bacilli 1

Clinical response assessment:

• Fever should resolve within 2-3 days after initiating antibiotics 1, 3
• Assess clinical response at day 2-3 for outpatients 1, 3
• If no improvement by day 5-7, consider further investigation rather than automatically extending antibiotic duration 1

Common Pitfalls to Avoid

Do not use macrolide monotherapy if:

• Patient has any comorbidities (COPD, diabetes, chronic heart/liver/renal disease, malignancy) 1, 2
• Local pneumococcal macrolide resistance is ≥25% 1, 2, 3
• Patient has recent antibiotic use within 3 months 1, 2

Do not automatically extend therapy:

• Beyond 7 days in responding patients without specific indications, as this increases resistance risk without improving outcomes 1, 2

Drug-specific contraindications:

• Doxycycline should be avoided in pregnancy 3
• Fluoroquinolones should be avoided in patients with chronic heart disease or heart failure due to risk of cardiac arrhythmias 3

When to Consider Hospitalization

Hospitalize if patient has:

• CURB-65 score ≥2 (Confusion, Urea >7 mmol/L, Respiratory rate ≥30, Blood pressure <90/60, Age ≥65) 2
• Multilobar infiltrates on chest radiograph 2
• Respiratory rate >24 breaths/minute 2
• Inability to maintain oral intake 2
• Oxygen saturation <90% on room air 2