What is the recommended IV antibiotic treatment for a patient with community-acquired pneumonia (CAP)?

IV Antibiotic Treatment for Community-Acquired Pneumonia

For hospitalized patients with community-acquired pneumonia not requiring ICU admission, use ceftriaxone 1-2 g IV daily PLUS azithromycin 500 mg IV daily, which provides comprehensive coverage for both typical bacterial pathogens and atypical organisms with strong evidence supporting reduced mortality. 1, 2

Non-ICU Hospitalized Patients (Standard Regimen)

Preferred combination therapy:

• Ceftriaxone 1-2 g IV once daily PLUS azithromycin 500 mg IV daily 1, 2
• Alternative β-lactams: Cefotaxime 1-2 g IV every 8 hours OR ampicillin-sulbactam 3 g IV every 6 hours, always combined with azithromycin 1

Alternative monotherapy:

• Levofloxacin 750 mg IV daily OR moxifloxacin 400 mg IV daily 1, 3
• Respiratory fluoroquinolone monotherapy demonstrates equivalent efficacy to β-lactam/macrolide combinations with fewer treatment discontinuations 1, 3

Critical timing:

• Administer the first antibiotic dose immediately in the emergency department—delays beyond 8 hours increase 30-day mortality by 20-30% 1, 4, 2

ICU Patients (Severe CAP)

Mandatory combination therapy—monotherapy is never adequate for ICU-level severity:

• 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 1, 4
• Alternative: β-lactam PLUS levofloxacin 750 mg IV daily OR moxifloxacin 400 mg IV daily 1, 4

Systemic corticosteroids:

• Administer within 24 hours of severe CAP development to reduce 28-day mortality 2

Special Pathogen Coverage

Add antipseudomonal coverage ONLY when risk factors present:

• Risk factors: Structural lung disease (bronchiectasis), recent hospitalization with IV antibiotics within 90 days, prior P. aeruginosa isolation 5, 1, 4
• Regimen: Piperacillin-tazobactam 4.5 g IV every 6 hours OR cefepime 2 g IV every 8 hours OR imipenem 500 mg IV every 6 hours OR meropenem 1 g IV every 8 hours PLUS ciprofloxacin 400 mg IV every 8 hours OR levofloxacin 750 mg IV daily PLUS aminoglycoside (gentamicin OR tobramycin 5-7 mg/kg IV daily) PLUS azithromycin 500 mg IV daily 5, 1, 4

Add MRSA coverage ONLY when risk factors present:

• Risk factors: Prior MRSA infection/colonization, recent hospitalization with IV antibiotics within 90 days, post-influenza pneumonia, cavitary infiltrates on imaging 5, 1, 4
• Regimen: Vancomycin 15 mg/kg IV every 8-12 hours (target trough 15-20 mg/mL) OR linezolid 600 mg IV every 12 hours added to base regimen 5, 1, 4

Transition to Oral Therapy

Switch from IV to oral when ALL criteria met:

• Hemodynamically stable (systolic BP ≥90 mmHg, heart rate ≤100 bpm) 1
• Clinically improving with temperature ≤37.8°C 1
• Able to take oral medications with normal GI function 1, 6
• Typically occurs by day 2-3 of hospitalization 1, 4

Oral step-down options:

• Amoxicillin 1 g orally three times daily PLUS azithromycin 500 mg orally daily 1
• Amoxicillin-clavulanate 875/125 mg orally twice daily PLUS azithromycin 500 mg orally daily 1
• Levofloxacin 750 mg orally daily OR moxifloxacin 400 mg orally daily 1

Duration of Therapy

Standard duration:

• Minimum 5 days AND until afebrile for 48-72 hours with no more than one sign of clinical instability 1, 4, 6, 2
• Typical duration for uncomplicated CAP: 5-7 days total 1, 4, 2
• FDA-approved azithromycin duration: 7-10 days total (IV followed by oral) 6

Extended duration (14-21 days) required for:

• Legionella pneumophila 1, 4
• Staphylococcus aureus 1, 4
• Gram-negative enteric bacilli 1, 4

Diagnostic Testing Before Antibiotics

Obtain in ALL hospitalized patients:

• Blood cultures (two sets from separate sites) 1, 4
• Sputum Gram stain and culture 1, 4
• COVID-19 and influenza testing when viruses are circulating in the community 2
• Urinary antigen testing for Legionella pneumophila serogroup 1 in severe CAP or ICU patients 1

Critical Pitfalls to Avoid

Never use macrolide monotherapy in hospitalized patients:

• Provides inadequate coverage for typical bacterial pathogens like S. pneumoniae 1, 4
• Macrolide resistance now exceeds 25% in most regions 1, 4

Do not add broad-spectrum coverage without documented risk factors:

• Antipseudomonal agents should only be used when specific risk factors present—not routinely 1, 4
• MRSA coverage should only be added when specific risk factors present—not routinely 1, 4

Do not extend therapy beyond 7 days in responding patients without specific indications:

• Increases antimicrobial resistance risk without improving outcomes 1

For penicillin-allergic patients:

• Use respiratory fluoroquinolone (levofloxacin OR moxifloxacin) as preferred alternative 1, 4
• For ICU patients with fluoroquinolone allergy: aztreonam 2 g IV every 8 hours PLUS azithromycin 500 mg IV daily 1