What is the recommended antibiotic treatment for pneumonia?

Antibiotic Treatment for Pneumonia

For outpatient community-acquired pneumonia without risk factors, amoxicillin 3 g/day orally is the first-line treatment for suspected pneumococcal infection, while macrolides (azithromycin or clarithromycin) are preferred for atypical pathogens or patients under 40 years old. 1, 2

Outpatient Community-Acquired Pneumonia (CAP)

Previously Healthy Patients Without Recent Antibiotic Use

• Amoxicillin 3 g/day orally is the preferred first-line agent for adults over 40 years with suspected pneumococcal pneumonia 1, 2
• Macrolides (azithromycin or clarithromycin) are recommended for adults under 40 years without underlying disease, particularly when atypical pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae) are suspected 1
• Azithromycin dosing: 500 mg on Day 1, then 250 mg daily on Days 2-5 3
• Treatment duration should be 14 days for outpatient pneumonia 1

Patients With Comorbidities or Recent Antibiotic Use

• Respiratory fluoroquinolone (levofloxacin 750 mg daily or moxifloxacin) as monotherapy 1, 2, 4
• Alternative: Amoxicillin-clavulanate or 2nd/3rd generation cephalosporin plus a macrolide 1
• The broader spectrum is necessary due to increased risk of resistant S. pneumoniae and gram-negative organisms 1

Hospitalized Patients (Non-ICU)

Combined therapy with a beta-lactam plus macrolide or respiratory fluoroquinolone monotherapy is recommended for non-severe hospitalized CAP. 1, 2, 4

Recommended Regimens

• Ceftriaxone or cefotaxime plus azithromycin 1, 2
• Ampicillin-sulbactam plus macrolide 1
• Levofloxacin 750 mg daily or moxifloxacin as monotherapy 1, 2
• Treatment duration: 7-10 days for most cases 1, 2

Switching to Oral Therapy

• Switch from IV to oral antibiotics after clinical improvement (typically within 48-72 hours) and when patient can tolerate oral medications 1, 4
• Use the same antibiotic class when switching (e.g., IV levofloxacin to oral levofloxacin) 5

Severe CAP Requiring ICU Admission

Combination therapy with a broad-spectrum beta-lactam plus either azithromycin or a respiratory fluoroquinolone is mandatory for severe pneumonia. 1, 2, 4

Standard Severe CAP (No Pseudomonas Risk)

• Ceftriaxone or cefotaxime plus azithromycin 1, 2
• Alternative: Beta-lactam plus levofloxacin 750 mg daily or moxifloxacin 1, 2
• Treatment duration: 10 days minimum 1, 2

Severe CAP With Pseudomonas Risk Factors

Risk factors include: structural lung disease, recent hospitalization, recent broad-spectrum antibiotics 1, 2

• Antipseudomonal beta-lactam (piperacillin-tazobactam, cefepime, imipenem, or meropenem) 1, 2, 4
• PLUS ciprofloxacin or levofloxacin 750 mg 1, 2
• OR PLUS aminoglycoside (gentamicin, tobramycin, or amikacin) plus azithromycin 1, 2, 4

MRSA Risk Factors Present

• Add vancomycin or linezolid to the above regimens 2, 4
• MRSA risk factors: prior MRSA infection, IV drug use, recent hospitalization 2, 4

Pathogen-Specific Treatment

Mycoplasma pneumoniae

• Azithromycin (500 mg Day 1, then 250 mg Days 2-5) 1, 3
• Alternatives: Doxycycline 100 mg twice daily for 7-14 days, or levofloxacin 750 mg daily 1, 2
• Important caveat: Macrolide resistance exceeds 90% in some Asian regions; consider fluoroquinolones or tetracyclines in these areas 1

Legionella Species

• Levofloxacin 750 mg daily is preferred over macrolides due to more rapid defervescence and shorter hospital stays 1, 2
• Alternative: Azithromycin 500 mg daily 1, 2
• Treatment duration: 7-10 days for immunocompetent patients, 21 days for immunosuppressed or severely ill patients 1, 2
• Rifampin combination therapy may be considered only for severe disease or immunocompromised patients refractory to monotherapy 1

Chlamydophila pneumoniae

• Azithromycin is preferred when confirmed 1
• Alternatives: Fluoroquinolones, other macrolides, or tetracyclines 1
• Treatment duration: 5 days for azithromycin, 10 days for other agents 1

Haemophilus influenzae

• Second or third generation cephalosporin or fluoroquinolone due to 25-50% beta-lactamase production 1
• Amoxicillin-clavulanate is effective for all strains including beta-lactamase producers 1
• Avoid: Ampicillin or amoxicillin alone unless susceptibility confirmed 1
• Important caveat: Levofloxacin resistance increased from 2% to 24% in Taiwan between 2004-2010; consider local resistance patterns 1

Moraxella catarrhalis

• Amoxicillin-clavulanate (97.8% of isolates produce beta-lactamase) 1
• Alternatives: Second/third generation cephalosporins or fluoroquinolones 1

Hospital-Acquired Pneumonia (HAP)

Low Risk of Mortality, No MRSA Risk

• Single-agent therapy: Piperacillin-tazobactam, cefepime, levofloxacin, imipenem, or meropenem 2

High Risk of Mortality or Recent IV Antibiotics

• Two antipseudomonal agents plus MRSA coverage (vancomycin or linezolid) 2
• Treatment duration: 10 days generally appropriate 2
• Extended therapy (14-21 days) for Legionella, staphylococcal, or gram-negative enteric bacilli 2

Critical Pitfalls and Caveats

Timing of Antibiotic Administration

• Antibiotics must be initiated immediately upon diagnosis of pneumonia 1, 2
• Delayed administration in severe pneumonia significantly increases mortality 2

Assessment of Treatment Response

• Evaluate clinical response at 48-72 hours after initiation 1
• Do not change antibiotics within the first 72 hours unless clinical deterioration occurs 1
• Fever should resolve within 24 hours for pneumococcal pneumonia, but may take 2-4 days for other etiologies 1

Resistance Considerations

• Macrolide resistance in M. pneumoniae is extremely high (up to 95%) in Asia; use fluoroquinolones or tetracyclines in these regions 1
• Fluoroquinolone resistance in H. influenzae has increased significantly; consider local resistance patterns 1
• Always consider penicillin-resistant S. pneumoniae in patients with risk factors (recent antibiotics, comorbidities) 1

QT Prolongation Risk

• Azithromycin and fluoroquinolones can prolong QT interval and cause torsades de pointes 3
• Exercise caution in patients with: known QT prolongation, bradyarrhythmias, uncompensated heart failure, hypokalemia, hypomagnesemia, or concurrent use of Class IA/III antiarrhythmics 3
• Elderly patients are more susceptible to QT prolongation effects 3

Inadequate Initial Coverage

• Failure to recognize severity leads to inadequate initial therapy and worse outcomes 2
• In severe pneumonia, always use combination therapy rather than monotherapy 1, 2, 4
• Never use beta-lactam monotherapy for severe CAP due to lack of atypical pathogen coverage 1, 2