What is the recommended dosage of amoxicillin for mild to moderate infections?

Amoxicillin Dosage for Mild to Moderate Infections

For adults with mild to moderate infections, amoxicillin 500 mg every 12 hours or 250 mg every 8 hours is recommended, while pediatric patients ≥3 months and <40 kg should receive 25 mg/kg/day divided every 12 hours or 20 mg/kg/day divided every 8 hours. 1, 2

Adult Dosing

For mild to moderate ear/nose/throat, skin/skin structure, or genitourinary tract infections, the standard dose is 500 mg every 12 hours or 250 mg every 8 hours. 2

• The maximum daily dose should not exceed 4000 mg/day 1
• Treatment should continue for a minimum of 48-72 hours beyond symptom resolution or evidence of bacterial eradication 2
• For infections caused by Streptococcus pyogenes, at least 10 days of treatment is required to prevent acute rheumatic fever 2

Site-Specific Adult Dosing:

• Dental infections: 500 mg three times daily for 7-10 days 1
• Lower respiratory tract infections (mild to moderate): 875 mg every 12 hours or 500 mg every 8 hours 2
• Acute bacterial rhinosinusitis: 1.5-4 g/day, with lower doses for mild disease without recent antibiotic use 1

Pediatric Dosing (≥3 months and <40 kg)

For mild to moderate infections, use 25 mg/kg/day divided every 12 hours or 20 mg/kg/day divided every 8 hours. 1, 2

• For severe infections or lower respiratory tract infections, increase to 45 mg/kg/day divided every 12 hours or 40 mg/kg/day divided every 8 hours 2
• High-dose regimens (90 mg/kg/day) are reserved for children at risk for penicillin-resistant S. pneumoniae in acute bacterial rhinosinusitis 1
• At least 10 days of treatment is required for Streptococcus pyogenes infections 2

Infants <12 Weeks (3 months)

• Maximum dose is 30 mg/kg/day divided every 12 hours due to incompletely developed renal function 2
• Treatment duration follows the same 48-72 hour rule beyond symptom resolution 2

Renal Impairment Dosing

Patients with severe renal impairment require dose adjustments: 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 an additional dose during and at the end of dialysis
• Patients with GFR <30 mL/min should NOT receive the 875 mg dose 2

Administration Considerations

Amoxicillin should be taken at the start of a meal to minimize gastrointestinal intolerance. 2

• Twice-daily dosing (every 12 hours) is as effective as three-times-daily dosing (every 8 hours) for lower respiratory tract infections and may result in less diarrhea 3
• For oral suspension, shake well before using and refrigerate (though not required); discard unused portion after 14 days 2

Special Populations

• Pregnancy: Category B, compatible with use during pregnancy 1
• Breastfeeding: Minimal risk to infant, compatible with breastfeeding but use with caution as it distributes into milk 1

Common Pitfalls

The standard dosing may be insufficient for severe infections or resistant pathogens—only 65% of hospitalized patients reached the pharmacodynamic target (40% time above MIC) with standard dosing for bacteria with MIC of 8 mg/L 4. However, for mild to moderate community infections, standard dosing remains appropriate as these typically involve more susceptible organisms 2.