Amoxicillin Dosing for Skin Infections
For skin infections in adults, amoxicillin should be dosed at 500 mg three times daily or 875 mg twice daily for 7-10 days. 1, 2
Dosing Guidelines
Adults (≥40 kg):
- First-line dosing:
- 500 mg orally every 8 hours (three times daily) OR
- 875 mg orally every 12 hours (twice daily)
- Duration: 7-10 days (minimum treatment should continue 48-72 hours after patient becomes asymptomatic)
Children (3 months to <40 kg):
- Mild to moderate infections: 25 mg/kg/day divided every 12 hours OR 20 mg/kg/day divided every 8 hours
- Severe infections: 45 mg/kg/day divided every 12 hours OR 40 mg/kg/day divided every 8 hours
- Duration: 7-10 days
Infants (<3 months):
- Maximum of 30 mg/kg/day divided every 12 hours due to incompletely developed renal function 2
Renal Dosing Adjustments
For patients with impaired renal function:
- GFR 10-30 mL/min: 500 mg or 250 mg every 12 hours (depending on infection severity)
- GFR <10 mL/min: 500 mg or 250 mg every 24 hours (depending on infection severity)
- Hemodialysis patients: 500 mg or 250 mg every 24 hours plus additional dose during and after dialysis 2
Clinical Considerations
Pathogen Coverage
Amoxicillin alone has excellent activity against streptococci but limited coverage against staphylococci, which are common causes of skin infections. Many Staphylococcus aureus strains produce beta-lactamases, with resistance rates to penicillin/amoxicillin approaching 89.5% 3.
Important Caveats
- Amoxicillin monotherapy is not recommended for skin infections where Staphylococcus aureus is likely to be present 1
- For skin infections, amoxicillin-clavulanate is generally preferred over amoxicillin alone due to better coverage against beta-lactamase producing organisms 4, 5
- For suspected methicillin-resistant Staphylococcus aureus (MRSA) infections, alternative agents should be considered
Alternative Regimens for Skin Infections
If amoxicillin alone must be used (e.g., due to clavulanate intolerance), consider:
- Adding dicloxacillin 500 mg four times daily to amoxicillin for better staphylococcal coverage 1
- For penicillin-allergic patients, consider clindamycin 300-450 mg three times daily 1, 6
Special Situations
- Human or animal bites: Amoxicillin-clavulanate is preferred over amoxicillin alone due to the polymicrobial nature of these infections 1, 6
- Erysipeloid: Amoxicillin 500 mg three times daily is specifically recommended 1
Monitoring
- Clinical response should be evident within 48-72 hours of starting therapy
- If no improvement is seen, consider culture and sensitivity testing and potential antibiotic change
Remember that while amoxicillin can be used for certain skin infections, particularly those caused by susceptible streptococci, amoxicillin-clavulanate provides broader coverage and is generally more appropriate for most skin and soft tissue infections.