Amoxicillin Dosing Recommendations
For adults, standard amoxicillin dosing is 500 mg three times daily, but high-dose therapy (90 mg/kg/day up to 4 g/day in two divided doses) is preferred for respiratory infections to overcome resistant Streptococcus pneumoniae. For children, standard dosing is 40-45 mg/kg/day, but high-dose therapy at 90 mg/kg/day in two divided doses is recommended for acute otitis media and community-acquired pneumonia 1, 2, 3, 4.
Adult Dosing
Standard Infections
- Standard dose: 500 mg orally three times daily 5
- High-dose regimen: 90 mg/kg/day (maximum 4 g/day) in two divided doses for respiratory tract infections 3, 4
- Duration: Typically 5-7 days for uncomplicated infections in adults 4
Specific Indications
For acute bacterial rhinosinusitis, amoxicillin-clavulanate is preferred over amoxicillin alone, with high-dose formulation (2 g orally twice daily) recommended when penicillin-resistant S. pneumoniae is suspected 4. For community-acquired pneumonia, amoxicillin 90 mg/kg/day in two divided doses (maximum 4 g/day) is the preferred oral agent 2.
For Lyme disease, amoxicillin 500 mg three times daily is an effective first-line oral option 5.
Pediatric Dosing
Standard Dosing by Age
- Children ≥3 months: 40-45 mg/kg/day in divided doses for standard infections 6
- High-dose therapy: 90 mg/kg/day in two divided doses for otitis media and pneumonia 1, 2
- Maximum daily dose: Should not exceed adult doses 1
Specific Pediatric Indications
For acute otitis media, the WHO recommends 40 mg/kg twice daily for 5 days 6, though IDSA guidelines support 90 mg/kg/day in two doses 1. For community-acquired pneumonia in children ≥5 years, 90 mg/kg/day in two doses is recommended 2.
For neonatal sepsis, amoxicillin 50 mg/kg/day in three divided doses combined with gentamicin is a first-choice regimen 7.
Renal Impairment Dosing
In renal impairment, dosing intervals must be extended rather than reducing individual doses to maintain therapeutic concentrations. Current dose reduction recommendations may lead to subtherapeutic levels 8, 9.
Dosing Adjustments by Creatinine Clearance
- CrCl 10-30 mL/min: 250-500 mg every 12 hours 10
- CrCl <10 mL/min: 250-500 mg every 24 hours 10
- Hemodialysis: 250-500 mg every 24 hours, with an additional dose during and after dialysis (half-life on dialysis is 3.6 hours) 9, 11
Critical Considerations in Renal Impairment
The serum half-life correlates strongly with creatinine clearance (r=0.967), increasing from 71 minutes at CrCl 100 mL/min to 16 hours in anephric patients 9. Maintain standard individual doses (not reduced) but extend dosing intervals to avoid subtherapeutic concentrations while preventing accumulation 8, 9.
For critically ill patients with augmented renal clearance (CrCl >130 mL/min), standard dosing often results in subtherapeutic levels. Consider increasing frequency to every 4 hours or using continuous infusion for severe infections 12, 13.
Important Caveats
Pregnancy and Lactation
Amoxicillin is safe in pregnancy and lactation, with dosing identical to non-pregnant patients 5. Doxycycline should be avoided as an alternative in these populations.
Drug Interactions
Probenecid decreases renal tubular secretion of amoxicillin, increasing serum levels 10. Oral contraceptive efficacy may be reduced; advise backup contraception 10.
Therapeutic Drug Monitoring
In critically ill patients, especially those with renal impairment or augmented renal clearance, therapeutic drug monitoring is essential to optimize dosing and prevent treatment failure 14, 13.
Common Pitfall
The most critical error is reducing individual doses in renal impairment rather than extending intervals. This leads to subtherapeutic concentrations and treatment failure, particularly against less susceptible pathogens with MICs of 4-8 mg/L 8. Always maintain adequate individual doses and adjust frequency based on renal function.