Management of Community-Acquired Pneumonia in Healthy Adults
For an otherwise healthy adult with community-acquired pneumonia, no drug allergies, no recent hospitalization, and no immunosuppression, the management approach depends primarily on severity and treatment setting.
Outpatient Management (Mild CAP)
First-Line Antibiotic Selection
Amoxicillin 1 g orally three times daily for 5–7 days is the preferred first-line therapy for previously healthy outpatients without comorbidities, providing superior pneumococcal coverage against 90–95% of Streptococcus pneumoniae isolates including many penicillin-resistant strains 1, 2.
Doxycycline 100 mg orally twice daily for 5–7 days serves as an acceptable alternative when amoxicillin cannot be used, offering coverage of both typical and atypical pathogens 1.
Macrolide monotherapy (azithromycin or clarithromycin) should be avoided in most U.S. regions because pneumococcal macrolide resistance rates of 20–30% exceed the 25% threshold at which macrolides become unsafe as first-line agents 1, 3.
Treatment Duration and Monitoring
Treat for a minimum of 5 days and continue until the patient is afebrile for 48–72 hours with no more than one sign of clinical instability 1, 3.
Arrange a clinical review at 48 hours (or sooner if symptoms worsen) to assess symptom resolution, oral intake, and treatment response 1.
If amoxicillin monotherapy fails by day 2–3, add or substitute a macrolide (azithromycin or clarithromycin) to cover atypical pathogens (Mycoplasma, Chlamydophila, Legionella) 1.
If combination therapy fails, switch to a respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) 1.
Inpatient Management (Non-ICU)
Standard Empiric Regimen
Ceftriaxone 1–2 g IV once daily PLUS azithromycin 500 mg IV or oral daily is the guideline-recommended regimen for hospitalized patients without ICU-level severity, providing comprehensive coverage for typical bacterial pathogens and atypical organisms 4, 1, 2.
Alternative β-lactams include cefotaxime 1–2 g IV every 8 hours or ampicillin-sulbactam 3 g IV every 6 hours, always combined with a macrolide 4.
Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg IV daily or moxifloxacin 400 mg IV daily) is equally effective but should be reserved for penicillin-allergic patients due to FDA warnings about serious adverse events 4, 1.
Critical Timing
Administer the first antibiotic dose in the emergency department immediately upon diagnosis; delays beyond 8 hours increase 30-day mortality by 20–30% 1, 3, 2.
Obtain blood cultures and sputum Gram stain/culture before initiating antibiotics in all hospitalized patients to enable pathogen-directed therapy 4, 1.
Transition to Oral Therapy
Switch from IV to oral antibiotics when the patient is hemodynamically stable (systolic BP ≥90 mmHg, heart rate ≤100 bpm), clinically improving, afebrile for 48–72 hours, respiratory rate ≤24 breaths/min, oxygen saturation ≥90% on room air, and able to take oral medications—typically by hospital day 2–3 4, 1.
Oral step-down options include amoxicillin 1 g three times daily plus azithromycin 500 mg daily 1.
Severe CAP Requiring ICU Admission
Mandatory Combination Therapy
Ceftriaxone 2 g IV daily (or cefotaxime 1–2 g IV every 8 hours or ampicillin-sulbactam 3 g IV every 6 hours) PLUS azithromycin 500 mg IV daily OR a respiratory fluoroquinolone (levofloxacin 750 mg IV daily or moxifloxacin 400 mg IV daily) is required for all ICU patients; β-lactam monotherapy is associated with higher mortality 4, 1, 3.
Combination therapy provides synergistic pathogen coverage and reduces mortality in critically ill patients with bacteremic pneumococcal pneumonia 1, 5.
Duration of Therapy
Minimum treatment duration is 5 days, continuing until the patient is afebrile for 48–72 hours with no more than one sign of clinical instability 4, 1, 3.
Extended courses of 14–21 days are reserved only for infections caused by Legionella pneumophila, Staphylococcus aureus, or Gram-negative enteric bacilli 4, 1, 3.
Common Pitfalls to Avoid
Never use macrolide monotherapy in hospitalized patients—it provides inadequate coverage for typical bacterial pathogens like S. pneumoniae and is associated with treatment failure 1.
Avoid indiscriminate fluoroquinolone use in uncomplicated outpatient CAP due to FDA warnings about serious adverse events (tendon rupture, peripheral neuropathy, aortic dissection) and rising resistance 1.
Do not add broad-spectrum antipseudomonal agents (piperacillin-tazobactam, cefepime) or MRSA coverage (vancomycin, linezolid) automatically—restrict to patients with documented risk factors such as structural lung disease, recent hospitalization with IV antibiotics within 90 days, prior Pseudomonas isolation, or post-influenza pneumonia 4, 1, 3.
Follow-Up and Prevention
Schedule a routine follow-up visit at 6 weeks; obtain a chest radiograph only if symptoms persist, physical signs remain abnormal, or the patient has high risk for underlying malignancy (e.g., smokers >50 years) 1.
Offer pneumococcal polysaccharide vaccine to all adults ≥65 years and those with high-risk conditions, and recommend annual influenza vaccination 4, 1.
Provide smoking-cessation counseling to all current smokers 4.