How should I initially manage an otherwise healthy adult outpatient with suspected community‑acquired pneumonia?

Initial Management of Community-Acquired Pneumonia in Healthy Adult Outpatients

For an otherwise healthy adult outpatient with suspected community-acquired pneumonia, start amoxicillin 1 g orally three times daily for 5–7 days immediately after clinical diagnosis, without requiring chest radiography or microbiological testing in most cases. 1

Confirming the Diagnosis

• Clinical diagnosis of CAP requires new respiratory symptoms (cough, dyspnea, pleuritic chest pain) plus at least one systemic feature (fever, chills, rigors) or new focal chest signs on examination 2
• Chest radiography is not mandatory for clinically stable outpatients who can be safely managed in the community; reserve imaging for patients with diagnostic uncertainty, failure to respond to therapy, or when complications are suspected 2
• Pulse oximetry should be performed in all suspected cases to identify hypoxemia (SpO₂ <92%) requiring hospital admission 2
• Routine microbiological investigations (blood cultures, sputum culture) are not recommended for outpatients; reserve sputum examination for patients who fail empirical therapy or when tuberculosis is suspected 2

Determining Outpatient Suitability

Use severity scoring to exclude patients requiring hospitalization:

• Apply CURB-65 score (Confusion, Urea >7 mmol/L, Respiratory rate ≥30/min, Blood pressure <90/60 mmHg, age ≥65 years): score ≥2 mandates hospital admission 1
• Alternatively, use Pneumonia Severity Index (PSI): classes I–III are appropriate for outpatient care, while classes IV–V require hospitalization 1
• Any severe feature mandates inpatient management: respiratory rate >30/min, oxygen saturation <92% on room air, multilobar infiltrates, inability to maintain oral intake, altered mental status, or unstable comorbid conditions 1

First-Line Antibiotic Selection

Previously Healthy Adults Without Comorbidities

• Amoxicillin 1 g orally three times daily for 5–7 days is the preferred first-line agent, providing coverage against 90–95% of Streptococcus pneumoniae isolates including many penicillin-resistant strains 1
• Doxycycline 100 mg orally twice daily for 5–7 days serves as an acceptable alternative, offering coverage of both typical and atypical pathogens 1
• Macrolide monotherapy (azithromycin 500 mg day 1, then 250 mg daily; or clarithromycin 500 mg twice daily) should only be used when local pneumococcal macrolide resistance is documented <25%—in most U.S. regions resistance is 20–30%, making monotherapy unsafe 1

Patients With Comorbidities or Recent Antibiotic Use

Comorbidities include: COPD, diabetes, chronic heart/liver/renal disease, malignancy, or antibiotic use within 90 days 1

• Option 1—Combination therapy: amoxicillin-clavulanate 875/125 mg twice daily PLUS azithromycin (500 mg day 1, then 250 mg daily) OR doxycycline 100 mg twice daily 1
• Option 2—Respiratory fluoroquinolone monotherapy: levofloxacin 750 mg daily OR moxifloxacin 400 mg daily for 5–7 days 1
• Both strategies provide coverage of typical pathogens (S. pneumoniae, H. influenzae) and atypical organisms (Mycoplasma, Chlamydophila, Legionella) 1

Treatment Duration and Monitoring

• Minimum duration: 5 days, continuing until afebrile for 48–72 hours with no more than one sign of clinical instability 1
• Standard duration for uncomplicated CAP: 5–7 days 1
• Mandatory clinical review at 48 hours (or sooner if indicated) to assess symptom resolution, oral intake, and treatment response 1

Indicators of Treatment Failure Requiring Hospital Referral

• No clinical improvement by day 2–3 1
• Development of respiratory distress, hypoxemia, or hemodynamic instability 1
• Inability to tolerate oral antibiotics (vomiting, GI dysfunction) 1
• New complications such as pleural effusion or sepsis 1

Escalation Strategy for Treatment Failure

• If amoxicillin monotherapy fails: add or substitute a macrolide to cover atypical pathogens 1
• If combination therapy fails: switch to a respiratory fluoroquinolone 1

Critical Pitfalls to Avoid

• Never use macrolide monotherapy in regions where pneumococcal macrolide resistance exceeds 25%—this increases risk of breakthrough bacteremia and treatment failure 1
• Avoid fluoroquinolones as first-line in uncomplicated outpatient CAP due to FDA warnings about serious adverse events (tendon rupture, peripheral neuropathy, aortic dissection) and rising resistance 1
• Do not routinely obtain chest radiographs for clinically stable outpatients, as this increases costs without improving outcomes 2
• If the patient received antibiotics within the previous 90 days, select an agent from a different class to minimize resistance 1

Follow-Up and Prevention

• Follow-up at 6 weeks for all patients; chest radiograph only for those with persistent symptoms, abnormal physical findings, or high risk for underlying malignancy (smokers >50 years) 1
• Offer pneumococcal polysaccharide vaccine to all adults ≥65 years and those with high-risk conditions 1
• Recommend annual influenza vaccination for all patients 1
• Provide smoking-cessation counseling to all current smokers 1