What is the recommended dose of amoxicillin (amoxicillin) for treating pneumonia in adults?

Amoxicillin Dosing for Pneumonia in Adults

For community-acquired pneumonia in adults, amoxicillin should be dosed at 1 gram orally every 8 hours (3 grams total daily), not the lower standard doses of 250-500 mg three times daily. 1

Outpatient Treatment Regimens

Otherwise Healthy Adults (No Comorbidities)

• Amoxicillin 1 g orally every 8 hours as monotherapy is the recommended regimen for previously healthy adults with community-acquired pneumonia 1, 2
• This high-dose regimen provides adequate coverage even against drug-resistant Streptococcus pneumoniae (DRSP) despite lacking activity against atypical organisms 1
• The FDA-approved adult dosing range is 750 to 1750 mg/day in divided doses every 8 to 12 hours 3

Adults with Comorbidities

• For patients with comorbidities (cardiopulmonary disease, diabetes, chronic kidney/liver disease, immunosuppression, or age ≥65 years), amoxicillin 1 g every 8 hours must be combined with a macrolide (azithromycin 500 mg daily or clarithromycin 500 mg twice daily) 1, 2
• This combination addresses the risk of mixed infections with atypical organisms (Mycoplasma pneumoniae, Chlamydophila pneumoniae, Legionella) which are common in this population 1

Alternative Beta-Lactam Option

• Amoxicillin-clavulanate 2000/125 mg twice daily can substitute for amoxicillin when beta-lactamase-producing organisms (H. influenzae, M. catarrhalis) are suspected 1
• This formulation provides enhanced coverage while maintaining the high amoxicillin dose needed for pneumococcal coverage 1

Hospitalized Patients (Non-Severe)

• For non-severe inpatients, use a beta-lactam plus macrolide combination: ampicillin-sulbactam 1.5-3 g every 6 hours, cefotaxime 1-2 g every 8 hours, or ceftriaxone 1-2 g daily PLUS azithromycin 500 mg daily or clarithromycin 500 mg twice daily 4
• Note that amoxicillin oral formulation is typically not the preferred beta-lactam for hospitalized patients requiring parenteral therapy 4

Treatment Duration

• Treat for 5-7 days in patients demonstrating clinical improvement 1
• Treatment should not routinely exceed 8 days in responding patients 1
• For severe pneumonia without identified pathogens, extend duration to 10 days 2

Critical Dosing Pitfalls to Avoid

Underdosing Risk

• Never use standard-dose amoxicillin (250-500 mg three times daily) for pneumonia, as this underdosing increases treatment failure risk and promotes antimicrobial resistance 1
• The high-dose regimen (1 g every 8 hours) is essential for achieving adequate serum and tissue concentrations against pneumococcal strains 5

Inappropriate Monotherapy

• Amoxicillin monotherapy should not be used in patients with comorbidities without adding atypical coverage, as mixed infections are common in this population 1
• Macrolide monotherapy should be avoided in areas with pneumococcal macrolide resistance ≥25%, but amoxicillin remains effective 1, 2

Recent Antibiotic Exposure

• Switch to a different antibiotic class if the patient received amoxicillin within the past 3 months to reduce resistance risk 1, 2
• This applies to any recent beta-lactam exposure, not just amoxicillin specifically 2

Contraindications and Limitations

• Amoxicillin should not be used for suspected MRSA or Pseudomonas aeruginosa pneumonia, as these require alternative coverage 1
• History of serious hypersensitivity reactions (anaphylaxis, Stevens-Johnson syndrome) to amoxicillin or other beta-lactams is an absolute contraindication 3
• For patients not improving on initial amoxicillin therapy, add or substitute a macrolide to cover atypical pathogens 2

Dose Adjustment in Renal Impairment

• Reduce the dose in patients with severe renal impairment (GFR <30 mL/min) 3
• The FDA label recommends dose reduction in elderly patients and those with renal failure, though specific adjustments for oral amoxicillin in pneumonia are not precisely defined in the guidelines 3