What is the second line treatment for dog bites?

Second-Line Treatment for Dog Bites

For dog bites, the second-line antibiotic treatment is doxycycline, with alternatives including fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin), second/third-generation cephalosporins, or carbapenems, depending on specific patient factors and suspected pathogens. 1

First-Line vs. Second-Line Treatment

First-Line Treatment

• Amoxicillin-clavulanate (875/125 mg twice daily) is the first-line treatment for dog bites due to its broad coverage against both aerobic and anaerobic bacteria commonly found in dog bites 1, 2
• For intravenous therapy, ampicillin-sulbactam or piperacillin-tazobactam are recommended first-line options 1

Second-Line Options (when first-line cannot be used)

1. Doxycycline (100 mg twice daily)

   • Excellent activity against Pasteurella multocida, which is commonly found in dog bites 1
   • Note that some streptococci may be resistant 1

2. Fluoroquinolones

   • Ciprofloxacin (500-750 mg twice daily oral; 400 mg every 12 hours IV)
   • Levofloxacin (750 mg daily oral or IV)
   • Moxifloxacin (400 mg daily oral or IV) - has good anaerobic coverage as monotherapy 1
   • Note: These may miss MRSA and some anaerobes unless combined with other agents 1

3. Second-generation cephalosporins

   • Cefuroxime (500 mg twice daily oral; 1 g every 12 hours IV) - good activity against P. multocida but misses anaerobes 1
   • Cefoxitin (1 g every 6-8 hours IV) 1

4. Third-generation cephalosporins

   • Ceftriaxone (1 g every 12-24 hours IV)
   • Cefotaxime (1-2 g every 6-8 hours IV) 1

5. Carbapenems (for severe infections or when other options are contraindicated) 1

   • Imipenem-cilastatin, meropenem, or ertapenem

Combination Therapy Options

For patients with penicillin allergies or when broader coverage is needed:

• Clindamycin (300 mg three times daily oral; 600 mg every 6-8 hours IV) plus a fluoroquinolone 1

  • Good coverage against staphylococci, streptococci, and anaerobes, but misses P. multocida 1

• Metronidazole (250-500 mg three times daily oral; 500 mg every 8 hours IV) plus a fluoroquinolone or trimethoprim-sulfamethoxazole

  • Metronidazole provides anaerobic coverage while the second agent covers aerobes 1

Special Considerations

Duration of Therapy

• For prophylaxis: 3-5 days
• For established infections: 7-14 days
• For complicated infections (osteomyelitis, septic arthritis): 3-4 weeks 2

Patient-Specific Factors to Consider

• Penicillin allergy: Choose doxycycline, fluoroquinolones, or clindamycin-based regimens
• Pregnancy: Avoid doxycycline and fluoroquinolones
• Children under 8: Avoid doxycycline when possible due to dental staining risk
• Immunocompromised patients: Consider broader coverage with carbapenems or combination therapy

Wound Characteristics

• Hand bites: Require more aggressive therapy due to higher infection risk
• Deep puncture wounds: May require longer duration of therapy
• Wounds with established infection: May need culture-guided therapy and possibly surgical debridement

Monitoring and Follow-up

• Assess response within 24-48 hours
• Monitor for signs of worsening infection (increasing erythema, pain, swelling, purulent discharge)
• Consider switching to oral therapy once infection is controlled if initially treated with IV antibiotics

Pitfalls to Avoid

• Not considering MRSA coverage in high-risk patients or areas with high MRSA prevalence
• Inadequate anaerobic coverage when using fluoroquinolones or trimethoprim-sulfamethoxazole alone
• Delaying treatment in high-risk wounds (hand, face, genital) or immunocompromised patients
• Forgetting tetanus prophylaxis if vaccination is not current within 10 years 2
• Overlooking rabies risk assessment based on geographic location and circumstances of the bite 2

Remember that wound cleaning, irrigation, and proper wound care remain essential components of dog bite management regardless of antibiotic choice.