Amoxicillin Dosing for Pneumonia
For community-acquired pneumonia in healthy adults without comorbidities, amoxicillin 1 gram orally three times daily (every 8 hours) is the first-line therapy recommended by the American Thoracic Society and Infectious Diseases Society of America. 1
Adult Dosing by Clinical Setting
Outpatient Treatment - No Comorbidities
- Amoxicillin 1 gram orally every 8 hours is the preferred first-line monotherapy for healthy adults, based on strong recommendation and moderate quality evidence 1
- Treatment duration should be 5-7 days for uncomplicated cases 1
- Continue therapy for at least 48-72 hours beyond clinical stability (afebrile, improving symptoms) 1, 2
Outpatient Treatment - With Comorbidities
- Combination therapy is required for patients with chronic heart disease, COPD, diabetes, or other comorbidities 1, 3
- Recommended regimen: Amoxicillin/clavulanate (Augmentin) 875 mg/125 mg twice daily PLUS azithromycin 500 mg day 1, then 250 mg daily for 5-7 days 1
- Alternative: Amoxicillin/clavulanate 875 mg/125 mg twice daily PLUS doxycycline 100 mg twice daily 3
High-Risk Situations Requiring Higher Doses
Use high-dose formulations when any of the following are present 1:
- Geographic area with pneumococcal macrolide resistance >25%
- Recent antibiotic use within 3 months
- Age >65 years
- Suspected penicillin-resistant S. pneumoniae (MIC ≥2 mg/L)
- Presence of comorbidities
Pediatric Dosing (≥3 Months and <40 kg)
Standard Dosing
- Mild/moderate infections: 25 mg/kg/day divided every 12 hours OR 20 mg/kg/day divided every 8 hours 2
- Severe infections or lower respiratory tract: 45 mg/kg/day divided every 12 hours OR 40 mg/kg/day divided every 8 hours 2
High-Dose for Resistant Organisms
- Amoxicillin/clavulanate 90 mg/kg/day (amoxicillin component) divided into 2 doses for drug-resistant S. pneumoniae or beta-lactamase producing organisms 1
Infants <3 Months
- Maximum 30 mg/kg/day divided every 12 hours due to incompletely developed renal function 2
Renal Impairment Dosing
Critical caveat: Patients with GFR <30 mL/min should NOT receive the 875 mg dose 2
Adjusted regimens 2:
- GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours
- GFR <10 mL/min: 500 mg or 250 mg every 24 hours
- Hemodialysis: 500 mg or 250 mg every 24 hours, with additional dose during and at end of dialysis
Extended Treatment Duration
Most cases require only 5-7 days, but extended treatment (14-21 days) is required ONLY for 1:
- Legionella pneumonia
- Staphylococcus aureus pneumonia
- Gram-negative enteric bacilli
Important Clinical Caveats
When Amoxicillin Monotherapy is Inappropriate
- Never use monotherapy in patients with comorbidities (chronic heart disease, COPD, diabetes, immunosuppression) 1, 3
- Avoid in hospitalized patients - these require IV beta-lactams (ceftriaxone, cefotaxime, or ampicillin-sulbactam) plus azithromycin or doxycycline 4, 3
Administration Considerations
- Take at the start of a meal to minimize gastrointestinal intolerance 2
- Oral suspension must be shaken well before use and discarded after 14 days 2
Alternative First-Line Options
- Doxycycline 100 mg twice daily is an acceptable alternative monotherapy for healthy outpatients, though with lower quality evidence (conditional recommendation) 4, 1
- Macrolides are acceptable ONLY if local pneumococcal macrolide resistance is documented <25% 1
Fluoroquinolone Caution
- Avoid fluoroquinolones in heart failure patients due to cardiac arrhythmia risk, despite being listed as an alternative for patients with comorbidities 3