What condition is treated with amoxicillin (amoxicillin) 500 mg three times a day (TID) for 7 days?

Amoxicillin 500 mg TID for 7 Days: Primary Indication

Amoxicillin 500 mg three times daily for 7 days is the first-line treatment for low-severity community-acquired pneumonia (CAP) in previously healthy adults without comorbidities. 1, 2

Clinical Context and Patient Selection

This regimen is specifically recommended for outpatients meeting the following criteria:

• CRB-65 score of 0-1 (indicating low severity pneumonia) 1
• No comorbidities such as COPD, diabetes, heart failure, renal disease, or malignancy 1, 2
• No recent antibiotic exposure within the past 3 months 1
• Age typically under 65 years without risk factors 3

Dosing Algorithm by Severity

Low-Severity CAP (Outpatient)

• Amoxicillin 500 mg to 1 gram orally every 8 hours for 5-7 days 1, 2
• This targets Streptococcus pneumoniae, the most common pathogen (48% of identified cases), with activity against 90-95% of pneumococcal strains 2

Patients With Comorbidities or Risk Factors

• Combination therapy required: Amoxicillin/clavulanate 875/125 mg twice daily PLUS azithromycin 500 mg day 1, then 250 mg daily for 5-7 days 1, 2
• Alternative: Respiratory fluoroquinolone monotherapy (levofloxacin 750 mg daily or moxifloxacin 400 mg daily) 1

Hospitalized Patients (Moderate-Severe CAP)

• Amoxicillin/clavulanate 1.2 grams IV every 8 hours PLUS macrolide, NOT plain amoxicillin 1
• Duration: 5-7 days for moderate severity, 7 days for ICU patients 1

Treatment Duration Considerations

The standard duration is 5-7 days, with recent evidence supporting shorter courses: 1, 2

• 3 days if clinical stability achieved by day 3 (afebrile for 48-72 hours, no more than one sign of clinical instability) 4
• 5 days if stability achieved by day 5 4
• 7 days for uncomplicated cases without early stability 1
• Extended to 14-21 days ONLY for Legionella, Staphylococcus aureus, or gram-negative enteric bacilli 2

Critical Pitfalls to Avoid

• Do NOT use this regimen for hospitalized patients - they require IV therapy with broader coverage 1
• Do NOT use in patients with recent antibiotic exposure (within 90 days) - select a different antibiotic class to reduce resistance risk 2
• Do NOT use monotherapy in patients with comorbidities - combination therapy or fluoroquinolone monotherapy is required 1, 2
• Do NOT extend duration beyond 7 days unless specific pathogens (Legionella, MRSA, gram-negative bacilli) are identified or complications occur 2, 4

Alternative Indications (Less Common)

Amoxicillin 500 mg TID for 7 days is also used for:

• Erysipeloid (skin infection from Erysipelothrix rhusiopathiae) 1
• Uncomplicated urinary tract infections due to vancomycin-resistant enterococci (VRE), though typically given every 8 hours 1

However, community-acquired pneumonia remains the primary and most common indication for this specific dosing regimen. 1, 2, 3