What is the recommended antibiotic regimen for a dog bite?

Antibiotic for Dog Bite

Amoxicillin-clavulanate is the first-line antibiotic for dog bite wounds, dosed at 875/125 mg twice daily for adults or 45 mg/kg/day divided every 12 hours for children. 1, 2, 3

Oral Antibiotic Regimens

First-Line Treatment

• Amoxicillin-clavulanate 875/125 mg twice daily is the preferred oral agent for outpatient management 1, 2, 4
• This combination provides coverage against the polymicrobial flora typical of dog bites, including Pasteurella species (present in 50% of dog bites), Staphylococcus aureus and Streptococcus species (each in ~40%), and anaerobes like Bacteroides, Fusobacterium, and Porphyromonas 1, 2

Alternative Oral Options (for penicillin allergy or intolerance)

• Doxycycline in standard doses has excellent activity against Pasteurella multocida 1, 2
• Moxifloxacin as monotherapy provides adequate coverage 2
• Clindamycin plus a fluoroquinolone (ciprofloxacin, levofloxacin, or moxifloxacin) covers both aerobic and anaerobic pathogens 1, 2
• Other fluoroquinolones or cefuroxime require addition of metronidazole or clindamycin for anaerobic coverage 1

Intravenous Options for Severe Infections

For patients requiring hospitalization due to systemic symptoms, moderate-to-severe infections, or high-risk wounds:

• Ampicillin-sulbactam 1, 2
• Piperacillin-tazobactam 1, 2
• Second-generation cephalosporins (cefoxitin) 1, 2
• Third-generation cephalosporins (ceftriaxone) plus metronidazole 2
• Carbapenems (ertapenem, imipenem, meropenem) 1, 2

Initial IV therapy should continue for 3-5 days, then transition to oral therapy when the patient is afebrile and showing clinical improvement 2

Treatment Duration

• Uncomplicated infections: 7-10 days total 2
• Septic arthritis: 3-4 weeks 1, 2
• Osteomyelitis: 4-6 weeks 1, 2

Critical Pitfalls to Avoid

Never use these antibiotics as monotherapy for dog bites:

• First-generation cephalosporins (cephalexin) have poor activity against Pasteurella multocida 1, 2
• Penicillinase-resistant penicillins (dicloxacillin) alone are inadequate 1, 2
• Macrolides (erythromycin) lack coverage for key pathogens 1, 2
• Clindamycin alone misses Pasteurella species 1, 2

High-Risk Situations Requiring Aggressive Management

Consider hospitalization and IV antibiotics for:

• Hand wounds, which are often more serious and prone to complications like septic arthritis and osteomyelitis 1, 2
• Immunocompromised patients or those with advanced liver disease (risk of Capnocytophaga canimorsus bacteremia and fatal sepsis) 1, 2
• Asplenic patients (particularly vulnerable to Capnocytophaga infection) 1, 2
• Wounds with suspected periosteal or joint capsule penetration (pain disproportionate to injury near bone/joint suggests this) 1, 2
• Pre-existing or resultant edema of the affected area 2

Adjunctive Wound Management

• Cleanse wounds thoroughly with sterile normal saline using copious irrigation with a 20-mL or larger syringe 1, 4
• Remove superficial debris; avoid aggressive debridement that enlarges the wound 1
• Do not close infected wounds 1
• Early closure (<8 hours) is controversial; approximation with Steri-Strips followed by delayed primary or secondary closure is prudent 1
• Facial wounds may be closed primarily by a plastic surgeon after meticulous wound care and prophylactic antibiotics 1
• Elevate injured extremities, especially if swollen 1
• Follow up within 24 hours by phone or office visit 1

Additional Considerations

• Tetanus prophylaxis should be updated if not current 2, 4
• Rabies prophylaxis may be indicated; consult local health officials 2, 4
• Most states require physicians to report animal bites by law 4