What are the recommended doses and courses of antibiotics for treating pneumonia?

Recommended Antibiotic Doses and Courses for Pneumonia Treatment

The standard treatment for pneumonia requires pathogen-specific antibiotics with dosing based on severity, with most cases requiring 5-7 days of therapy for uncomplicated infections and up to 14 days for severe or complicated cases. 1

Adult Treatment Regimens by Pathogen

Streptococcus pneumoniae

• Penicillin-susceptible (MIC <2):
  • Preferred: Amoxicillin 1g PO q8h, Penicillin G 2-3 MU IV q4h, or Ampicillin 2g IV q6h
  • Alternative: Ceftriaxone 1-2g IV q12h, Levofloxacin 750mg PO/IV daily, or Moxifloxacin 400mg PO/IV daily 2
  • Duration: 5-7 days for uncomplicated cases 1

Atypical Pathogens

• Mycoplasma pneumoniae:

  • Preferred: Doxycycline 100mg IV/PO q12h for 7-14 days
  • Alternative: Azithromycin 500mg PO day 1, then 250mg daily for 4 days 2, 3

• Legionella species:

  • Preferred: Levofloxacin 750mg IV/PO daily or Moxifloxacin 400mg IV/PO daily
  • Alternative: Azithromycin 1000mg IV day 1, then 500mg IV/PO daily 2
  • Duration: 7-10 days 2

Staphylococcus aureus

• MSSA:

  • Preferred: Oxacillin 2g IV q4-6h or Cefazolin 2g IV q8h
  • Alternative: Levofloxacin 750mg IV/PO daily 2

• MRSA:

  • Preferred: Vancomycin 15-20mg/kg IV q8-12h or Linezolid 600mg PO/IV q12h 2

Haemophilus influenzae

• β-lactamase negative:

  • Preferred: Amoxicillin 1g PO q8h 2

• β-lactamase positive:

  • Preferred: Amoxicillin/clavulanate 1.2g IV/PO q12h or Ceftriaxone 2g IV daily
  • Alternative: Levofloxacin 750mg IV/PO daily 2

Pseudomonas aeruginosa

• Combination therapy recommended:
  • Antipseudomonal β-lactam (Ceftazidime 1-2g IV q8-12h, Piperacillin/tazobactam 4.5g IV q6h, or Meropenem 1g IV q8h)
  • PLUS either Ciprofloxacin 400mg IV q12h or Amikacin 20mg/kg/day 2
  • Duration: 7 days 2
  • De-escalate to monotherapy once susceptibility results are available 2

Severity-Based Approach

Outpatient (Mild-Moderate)

• First-line: Levofloxacin 750mg PO daily for 5 days 1, 4
• Alternative: Amoxicillin 1g PO TID + Azithromycin 500mg PO day 1, then 250mg daily for 4 days 1, 3

Inpatient (Moderate-Severe)

• First-line: Ceftriaxone 1-2g IV daily + Azithromycin 500mg IV/PO daily 1
• Alternative: Levofloxacin 750mg IV daily as monotherapy 1, 4

ICU (Severe)

• High risk of mortality: Piperacillin-tazobactam 4.5g IV q6h OR Ceftriaxone 1-2g IV daily PLUS a macrolide 1
• Risk for Pseudomonas: Meropenem 1g IV q8h + antipseudomonal coverage 1
• MRSA risk: Add Vancomycin or Linezolid if prior IV antibiotics within 90 days or high MRSA prevalence 1

Pediatric Dosing

Community-Acquired Pneumonia

• Age >3 months:
  • 10mg/kg as single dose on day 1, followed by 5mg/kg on days 2-5 (azithromycin) 2, 3
  • For weight-based dosing, refer to pediatric guidelines 2

Duration of Therapy

• Standard duration: 5-7 days for most uncomplicated cases 1, 4
• Extended duration: 7-14 days for severe or complicated pneumonia 1
• Clinical stability criteria for considering therapy completion:
  • Temperature ≤37.8°C for 48 hours
  • Heart rate ≤100 beats/min
  • Respiratory rate ≤24 breaths/min
  • Systolic BP ≥90 mmHg
  • Oxygen saturation ≥90% on ambient air
  • Normal mental status
  • Ability to maintain oral intake 2

Switching from IV to Oral Therapy

Consider oral switch when:

• Improvement in cough and dyspnea
• Patient is afebrile
• Decreasing white blood cell count
• Functioning gastrointestinal tract with adequate oral intake
• Oxygen saturation >90% on ≤2L oxygen 1

Important Clinical Considerations

1. Pathogen-directed therapy is preferred when the causative organism is identified, but empiric therapy should not be delayed while awaiting culture results 1

2. High-dose, short-course fluoroquinolone therapy (e.g., levofloxacin 750mg daily for 5 days) has shown equivalent efficacy to traditional longer courses for community-acquired pneumonia 4

3. Combination therapy is recommended initially for suspected Pseudomonas infections, with de-escalation to monotherapy once susceptibility results are available 2

4. Clinical monitoring should be performed at least every 4 hours, with reassessment at 48-72 hours to evaluate treatment response 1

5. Treatment failure should prompt consideration of:

   • Resistant pathogens
   • Incorrect diagnosis
   • Complications (empyema, abscess)
   • Non-infectious causes 1

6. Beta-lactams remain highly effective for pneumococcal pneumonia even with in vitro resistance, with fewer documented treatment failures compared to fluoroquinolones and macrolides 5