What is the role of Amoxicillin (amoxicillin) in treating pneumonia?

From the Guidelines

Amoxicillin is a recommended first-line treatment for community-acquired pneumonia in appropriate patients, with a preferred dosage of 500 mg three times daily or 875 mg twice daily for 5-7 days, as suggested by the British Thoracic Society guidelines 1.

Key Considerations

• Amoxicillin works well against common pneumonia-causing bacteria, particularly Streptococcus pneumoniae, by inhibiting bacterial cell wall synthesis.
• However, it may not be effective against atypical pathogens or bacteria that produce beta-lactamase enzymes.
• In cases where atypical pathogens are suspected or the patient has risk factors for drug-resistant organisms, combination therapy with a macrolide (like azithromycin) or using amoxicillin-clavulanate instead may be more appropriate, as recommended by the Infectious Disease Society of America (IDSA) and the American Thoracic Society (ATS) 1.

Patient Factors to Consider

• Patients with penicillin allergy should not take amoxicillin and should inform their healthcare provider to receive an alternative antibiotic.
• Patients with chronic obstructive airway disease (COAD) may require additional considerations, such as the use of amoxicillin-clavulanate or second-generation cephalosporin, as recommended by the Canadian Community-Acquired Pneumonia Working Group 1.

Treatment Duration and Side Effects

• Patients should complete the full course of antibiotics even if symptoms improve before finishing treatment.
• Side effects may include diarrhea, nausea, and rash, as commonly seen with amoxicillin use 1.

Guideline Recommendations

• The European Respiratory Society and the revised national guidelines of South Africa also recommend aminopenicillins, such as amoxicillin, as first-line therapy for community-acquired pneumonia 1.
• The French guidelines recommend oral amoxicillin 3 g/day for adults with no risk factor and no sign of severity, with suspected pneumococcal origin 1.

From the FDA Drug Label

Infections of the Lower Respiratory Tract:Amoxicillin for oral suspension is indicated in the treatment of infections due to susceptible (ONLY β-lactamase–negative) isolates of Streptococcusspp. (α-and β-hemolytic isolates only), S. pneumoniae, Staphylococcusspp., or H. influenzae.

Amoxicillin is indicated for the treatment of lower respiratory tract infections, including those caused by Streptococcus pneumoniae, which is a common cause of pneumonia. The recommended dosage for lower respiratory tract infections is:

• 875 mg every 12 hours or 500 mg every 8 hours for adults
• 45 mg/kg/day in divided doses every 12 hours or 40 mg/kg/day in divided doses every 8 hours for pediatric patients aged 3 months and older and weight less than 40 kg 2.

From the Research

Amoxicillin for Pneumonia

• Amoxicillin is used to treat community-acquired pneumonia (CAP) in adults and children 3, 4, 5.
• The efficacy of amoxicillin in treating CAP has been compared to other antibiotics, such as penicillin, clarithromycin, and levofloxacin 3, 4.
• A study found that high-dose amoxicillin was superior to high-dose penicillin in treating uncomplicated CAP in adults 4.
• Another study found that amoxicillin was effective in treating CAP in children, with no significant difference in efficacy between a lower dose (35-50 mg/kg/day) and a higher dose (70-90 mg/kg/day) 5.
• The optimal duration of amoxicillin treatment for CAP in children is still unclear, with one study finding that 3-day and 7-day treatments were non-inferior to each other 5.

Diagnosis and Treatment of Pneumonia

• The diagnosis of CAP is based on history, physical examination, and chest x-ray 6.
• Appropriate diagnostic studies for patients with moderately-severe to severe pneumonia include sputum Gram's stain and culture, blood cultures, and acute serum sample 6.
• Initial therapy for patients requiring hospitalization includes a third-generation cephalosporin plus a macrolide or a quinolone 6.
• Macrolide resistance is common in Streptococcus pneumoniae, but the use of macrolides as part of a combination regimen for CAP is still recommended 7.

Antibiotic Resistance

• The use of antibiotics, including amoxicillin, can promote the emergence of resistant strains 6, 3.
• A study found that the use of azithromycin was associated with a reduction in in-hospital mortality in patients with CAP, despite high levels of macrolide resistance 7.
• The development of antibiotic resistance is a major concern, and further studies are needed to determine the optimal use of antibiotics for CAP 3, 5.