What alternative antibiotic can be used for cat bites if Augmentin (amoxicillin/clavulanate) is not suitable?

Alternative Antibiotics for Cat Bites When Augmentin is Not Suitable

Doxycycline is the recommended alternative antibiotic for cat bites when Augmentin (amoxicillin/clavulanate) is not suitable, due to its excellent activity against Pasteurella multocida, the most common pathogen in cat bite wounds. 1

First-Line Alternative Options

• Doxycycline (100 mg twice daily): Excellent coverage against Pasteurella multocida, which is present in 75% of cat bite wounds, as well as good activity against staphylococci and anaerobes 1, 2

• Fluoroquinolones + Metronidazole: For patients who cannot take doxycycline, a combination therapy may be used:

  • Ciprofloxacin (500-750 mg twice daily) or Levofloxacin (750 mg daily) for aerobic coverage 1
  • Plus Metronidazole (500 mg three times daily) for anaerobic coverage 1

• Trimethoprim-Sulfamethoxazole (TMP-SMX): Good activity against aerobes but has poor activity against anaerobes, so may need to be combined with metronidazole 1, 3

Second-Line Options (Intravenous)

For severe infections requiring intravenous therapy:

• Ampicillin-sulbactam: Effective against most pathogens in cat bites 1
• Piperacillin-tazobactam: Broad spectrum coverage but misses MRSA 1
• Second-generation cephalosporins (e.g., cefuroxime): Good activity against P. multocida but may miss anaerobes 1
• Carbapenems (e.g., ertapenem, imipenem): Broad spectrum but should be reserved for severe infections 1

Microbiology of Cat Bites

• Cat bites have a higher infection risk than dog bites due to their puncture-type wounds 1
• 75% of cat bite wounds contain Pasteurella multocida (vs. 50% in dog bites) 1
• 65% contain anaerobic bacteria (vs. 50% in dog bites) 1
• 40% contain staphylococci and streptococci 1
• Cat bites have a higher proportion of osteomyelitis and septic arthritis complications 1

Antibiotics to Avoid

• First-generation cephalosporins (e.g., cephalexin): Poor activity against P. multocida 1
• Penicillinase-resistant penicillins (e.g., dicloxacillin): Poor activity against P. multocida 1
• Macrolides (e.g., erythromycin): Poor activity against P. multocida 1
• Clindamycin alone: Misses P. multocida despite good activity against staphylococci, streptococci, and anaerobes 1, 4

Special Considerations

• Hand wounds from cat bites have the highest risk of infection and may require more aggressive therapy 5
• For immunocompromised patients, broader spectrum coverage may be needed 1
• Treatment duration is typically 5-7 days for uncomplicated infections 1
• For complications like osteomyelitis, 4-6 weeks of therapy may be required; for septic arthritis, 3-4 weeks 1

Treatment Algorithm

1. For mild infections in patients without penicillin allergy:

   • First choice: Doxycycline 100 mg twice daily 1
   • Alternative: TMP-SMX plus metronidazole 1

2. For moderate to severe infections:

   • Intravenous therapy with ampicillin-sulbactam, piperacillin-tazobactam, or a carbapenem 1
   • Consider adding vancomycin if MRSA is suspected 1

3. For penicillin-allergic patients:

   • Doxycycline (preferred) 1
   • Fluoroquinolone plus metronidazole 1

4. For hand wounds (higher risk):

   • Consider initial intravenous therapy even for seemingly mild infections 1
   • Prophylactic antibiotics have been shown to significantly reduce infection risk (NNT = 4) 6

Remember that proper wound care, including thorough irrigation and debridement if necessary, is as important as antibiotic therapy for preventing infection 1.