What is the initial treatment for pneumonia?

Initial Treatment for Pneumonia

For outpatients without comorbidities, start with amoxicillin 1 g three times daily or a macrolide (azithromycin); for hospitalized non-ICU patients, use a β-lactam (such as ceftriaxone) plus a macrolide (such as azithromycin); for severe ICU pneumonia, use a β-lactam plus either a macrolide or respiratory fluoroquinolone. 1, 2

Outpatient Treatment Algorithm

Previously Healthy Adults (No Comorbidities)

• Amoxicillin 1 g every 8 hours is the first-line therapy for patients without risk factors for drug-resistant pathogens 1, 2
• Alternatively, use a macrolide such as azithromycin (500 mg on Day 1, then 250 mg Days 2-5) or clarithromycin, particularly for patients under 40 years old or when atypical pathogens (Mycoplasma, Chlamydophila, Legionella) are suspected 1, 2
• Doxycycline 100 mg twice daily (with first dose of 200 mg) is another acceptable first-line option 2

Outpatients with Comorbidities or Recent Antibiotic Use

• Use combination therapy with a β-lactam plus a macrolide (e.g., amoxicillin plus azithromycin) 1, 2
• Alternatively, use a respiratory fluoroquinolone (levofloxacin or moxifloxacin) as monotherapy 1, 2
• Comorbidities to consider include chronic heart, lung, liver, or renal disease, diabetes, alcoholism, malignancy, or asplenia 3

Hospitalized Non-ICU Patients

• Standard regimen: β-lactam (ceftriaxone 1-2 g every 24 hours) PLUS a macrolide (azithromycin or clarithromycin) 1, 2, 4
• Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin or moxifloxacin) 1, 2
• Most patients can be adequately treated with oral antibiotics if able to tolerate oral intake 5
• When oral treatment is contraindicated, use intravenous ampicillin or benzylpenicillin plus erythromycin or clarithromycin 5
• Administer the first antibiotic dose while still in the emergency department, as early administration is associated with improved outcomes 2

Severe CAP/ICU Treatment

Without Risk Factors for Pseudomonas

• β-lactam (non-antipseudomonal cephalosporin such as ceftriaxone or cefotaxime) PLUS either a macrolide OR a respiratory fluoroquinolone 1, 2
• Alternative: Respiratory fluoroquinolone (moxifloxacin or levofloxacin) with or without a non-antipseudomonal cephalosporin 1

With Risk Factors for Pseudomonas

• Antipseudomonal β-lactam (cefepime, piperacillin-tazobactam, or carbapenem) PLUS either ciprofloxacin/levofloxacin OR aminoglycoside plus azithromycin 1, 2
• Risk factors for Pseudomonas include structural lung disease (bronchiectasis), recent hospitalization, or recent broad-spectrum antibiotic use 2

MRSA Coverage

• Add vancomycin or linezolid when community-acquired MRSA is suspected 2
• Risk factors include prior MRSA infection, recent hospitalization, or recent antibiotic use 2

Duration and Transition of Therapy

• Minimum duration is 5 days for most patients, with the patient required to be afebrile for 48-72 hours and have no more than one sign of clinical instability before discontinuing 1, 2
• Treatment should generally not exceed 8 days in a responding patient 1
• For uncomplicated S. pneumoniae pneumonia, 7-10 days is typically sufficient 2, 6
• Extend treatment to 14-21 days when Legionella, staphylococcal, or Gram-negative enteric bacilli are suspected or confirmed 5, 2

Switch to Oral Therapy

• Switch from IV to oral therapy when the patient is hemodynamically stable, clinically improving, able to take oral medications, and has a normally functioning GI tract 5, 3
• Up to half of all patients are eligible for switch therapy by hospital Day 3 5
• This can be done even in patients with positive blood cultures (except S. aureus, which requires longer IV therapy) 5
• Early switch to oral therapy can reduce hospital length of stay and may improve outcomes 5

Critical Pitfalls and Caveats

Fluoroquinolone Use

• Reserve respiratory fluoroquinolones for patients with β-lactam allergies or specific indications to prevent resistance development 2
• Despite concerns about adverse events (QT prolongation, tendon rupture, CNS effects), fluoroquinolones remain justified for adults with comorbidities due to their performance, low resistance rates, and coverage of both typical and atypical organisms 2, 7
• The FDA has issued warnings about increasing reports of adverse events related to fluoroquinolone use 2, 7

Atypical Pathogen Coverage

• Ensure coverage for atypical pathogens (Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella pneumophila) in all hospitalized patients 1, 2
• While research shows no mortality benefit from empirical atypical coverage, clinical success is significantly higher for Legionella when atypical antibiotics are used 2

Macrolide Resistance

• Consider S. pneumoniae resistance to macrolides, which ranges 30-40% and often co-exists with β-lactam resistance 2
• This is particularly important in patients with recent hospitalization, chronic diseases, or prior antibiotic exposure 2

Patients Who Fail to Improve

• Antibiotic therapy should not be changed within the first 72 hours unless there is marked clinical deterioration or bacteriologic data necessitate a change 5
• For patients who fail to improve by Day 3, conduct a careful review of clinical history, examination, prescription chart, and all available investigation results 5, 2
• Consider repeat chest radiograph, CRP, white cell count, and further microbiological testing 5, 2
• In severe pneumonia with radiographic deterioration and clinical worsening, aggressive evaluation and antibiotic change may be necessary before 72 hours 5

Clostridium Difficile Risk

• Be aware that C. difficile-associated diarrhea can occur with nearly all antibacterial agents, including azithromycin 7
• If CDAD is suspected, ongoing antibiotic use not directed against C. difficile may need to be discontinued 7