Co-amoxiclav Dosing for Skin Infections
For animal or human bite-related skin infections, co-amoxiclav (amoxicillin-clavulanate) should be dosed at 500-875 mg orally twice daily for 7-10 days, as it provides essential coverage against both aerobic and anaerobic bacteria including beta-lactamase producing organisms. 1
Primary Indication: Bite Wounds
Co-amoxiclav is specifically recommended by the Infectious Diseases Society of America (IDSA) as first-line therapy for animal and human bite wounds because it covers the polymicrobial flora typically involved in these infections, including Pasteurella multocida, Staphylococcus aureus, Streptococcus species, and anaerobes. 1
Standard Dosing Regimen
- Oral dose: 500 mg twice daily OR 875 mg twice daily 1, 2
- Duration: 7-10 days for established infections 1
- Prophylactic use: 3-5 days for high-risk bite wounds (immunocompromised patients, asplenic patients, advanced liver disease, significant edema, moderate-to-severe injuries especially to hand/face, or injuries penetrating periosteum/joint capsule) 1
Important Clinical Context
When Co-amoxiclav is NOT First-Line
For most non-bite skin infections (cellulitis, impetigo, abscesses), co-amoxiclav is not the preferred agent. The IDSA guidelines recommend:
- Non-purulent cellulitis without MRSA risk: Cephalexin 500 mg four times daily or other anti-streptococcal agents 3, 4
- Purulent infections or MRSA suspected: Trimethoprim-sulfamethoxazole, doxycycline, or clindamycin 3, 4
- Necrotizing infections: Broad-spectrum IV therapy (piperacillin-tazobactam, ampicillin-sulbactam, or carbapenems) plus vancomycin, with urgent surgical intervention 1
Critical Pitfall to Avoid
Do not use co-amoxiclav as empiric therapy for typical cellulitis or skin abscesses unless there is a specific indication (bite wound, mixed aerobic-anaerobic infection). 1 The drug provides unnecessary anaerobic coverage for most skin infections and has higher gastrointestinal side effect rates compared to simpler agents like cephalexin. 2, 5
Specific Clinical Scenarios
Animal Bites
- Co-amoxiclav 500-875 mg twice daily is the oral agent of choice 1
- Alternative IV option: Ampicillin-sulbactam 1.5-3.0 g every 6-8 hours 1
- Covers Pasteurella multocida (common in cat/dog bites), staphylococci, streptococci, and oral anaerobes 1
Human Bites
- Co-amoxiclav 500 mg every 8 hours (three times daily dosing may be preferred for human bites) 1
- Covers Eikenella corrodens and oral anaerobes characteristic of human oral flora 1
Mixed Aerobic-Anaerobic Infections
- When anaerobic coverage is specifically needed (foul-smelling discharge, tissue necrosis, proximity to mucosal surfaces) 1
- Co-amoxiclav provides this coverage, though IV options (piperacillin-tazobactam, ampicillin-sulbactam) are preferred for severe infections 1
Treatment Duration and Monitoring
- Standard duration: 7-10 days depending on clinical response 1
- Prophylaxis duration: 3-5 days for high-risk bite wounds 1
- Clinical response expected: Within 48-72 hours; if no improvement, consider resistant organisms, deeper infection, or alternative diagnosis 3
- Extend therapy beyond 7 days if infection has not adequately improved 1, 3
Safety and Tolerability
- Common side effects include nausea (9%) and diarrhea (9%), which are generally mild to moderate 2, 5
- Lower gastrointestinal side effects with twice-daily 875 mg formulation compared to three-times-daily 500 mg dosing 2
- Generally well-tolerated with low withdrawal rates for adverse effects 5