What is the recommended dose of amoxicillin (amoxicillin) for an adult patient with pneumonia, without severe allergies or contraindications?

Amoxicillin Dosing for Adult Pneumonia

For adults with community-acquired pneumonia without severe symptoms or risk factors, the recommended dose is amoxicillin 1 gram orally three times daily (total 3 grams/day) for 5-7 days. 1, 2

Standard Dosing Regimen

• Amoxicillin 1 g orally three times daily represents the preferred first-line therapy for previously healthy adults under 65 years without comorbidities, based on strong recommendation and moderate-quality evidence from the American Thoracic Society 2
• The French guidelines specify amoxicillin 3 g/day orally for adults over 40 years with suspected pneumococcal pneumonia without risk factors or serious symptoms 1
• This high-dose regimen (1 g TID) provides optimal coverage against Streptococcus pneumoniae, including penicillin-resistant strains with MIC ≤2 mg/mL 2

Treatment Duration

• Treat for a minimum of 5 days AND until the patient is afebrile for 48-72 hours with no more than one sign of clinical instability 2
• Typical duration for uncomplicated community-acquired pneumonia is 5-7 days once clinical stability is achieved 2
• The French guidelines recommend 7 days for patients without risk factors 1

When to Use Combination Therapy Instead

• Adults with comorbidities (COPD, diabetes, chronic heart/liver/renal disease, malignancy) require combination therapy with amoxicillin-clavulanate 875/125 mg twice daily PLUS azithromycin, rather than amoxicillin monotherapy 2, 3
• Patients over 65 years should receive amoxicillin-clavulanate 875/125 mg twice daily rather than plain amoxicillin 3
• Recent antibiotic use within 90 days necessitates selecting an agent from a different antibiotic class 2

Clinical Evidence Supporting This Dose

• The 3 g/day dose (1 g TID) covers 98% of pneumococcal infections in adults, with resistant strains found in only 2% of cases 4
• Clinical trials demonstrate complete resolution of fever, cough, and pleural pain within 3 days in 77% of patients treated with amoxicillin 1 g three times daily 5
• Recent population-level data from the UK showed no mortality difference between amoxicillin and co-amoxiclav for CAP treatment, supporting narrow-spectrum therapy when appropriate 6

Critical Pitfalls to Avoid

• Never use standard-dose amoxicillin (500 mg TID)—this provides insufficient pneumococcal coverage against resistant strains 2
• Do not use amoxicillin monotherapy for hospitalized patients requiring IV therapy—these patients need ceftriaxone plus azithromycin or respiratory fluoroquinolone 2
• Avoid macrolide monotherapy in areas where pneumococcal macrolide resistance exceeds 25%, as this leads to treatment failure 2
• Do not extend therapy beyond 7-8 days in responding patients without specific indications, as longer courses increase antimicrobial resistance risk 1, 2

When Hospitalization is Required

• If the patient requires hospitalization, switch to IV ceftriaxone 1-2 g daily PLUS azithromycin 500 mg daily, as amoxicillin alone is inadequate for hospitalized patients 2
• Administer the first antibiotic dose in the emergency department immediately, as delays beyond 8 hours increase 30-day mortality by 20-30% 2