Should Antibiotics Be Prescribed for Dog Bites?
Antibiotics should NOT be routinely prescribed for all dog bites—prescribe them only for high-risk wounds or when the patient presents within 24 hours with specific risk factors, but withhold antibiotics if the patient presents 24 hours or more after the bite without signs of infection. 1, 2
Risk Stratification Algorithm
The decision to prescribe antibiotics depends on timing of presentation and risk factors:
If Presenting WITHIN 24 Hours of Bite:
Prescribe prophylactic antibiotics (3-5 days) if ANY of the following high-risk features are present: 1, 2
- Wound location: Hand, foot, face, genitals, or near joints 1, 2
- Wound characteristics: Deep wounds, puncture wounds, wounds requiring primary closure, or wounds with significant tissue damage 2, 3, 4
- Patient factors: Immunocompromised status, diabetes, advanced liver disease, asplenia, prosthetic joints, or prosthetic heart valves 1, 2
- Anatomic concerns: Injuries that may have penetrated periosteum or joint capsule 2
Do NOT prescribe antibiotics for low-risk wounds: superficial wounds on the trunk or extremities (excluding hands/feet) in immunocompetent patients presenting early 1, 2
If Presenting 24 Hours or MORE After Bite:
Do NOT prescribe antibiotics unless there are clinical signs of infection (erythema, warmth, purulence, systemic symptoms). 1, 2 This is a critical guideline recommendation from the World Society of Emergency Surgery—prescribing antibiotics "just in case" at late presentation violates evidence-based guidelines and promotes antimicrobial resistance. 2
Antibiotic Selection
First-line oral agent: Amoxicillin-clavulanate 2, 5, 3, 4
This provides coverage against the polymicrobial flora of dog bites, which typically contains an average of 5 different bacterial species including Pasteurella species (50% of wounds), Staphylococcus aureus (40%), Streptococcus species (40%), and anaerobes. 2
Alternative oral options if amoxicillin-clavulanate is contraindicated: 2
- Doxycycline (excellent activity against Pasteurella multocida)
- Moxifloxacin as monotherapy
- Clindamycin plus a fluoroquinolone
For severe infections requiring IV therapy: 2
- Piperacillin-tazobactam
- Carbapenems (ertapenem, imipenem, meropenem)
- Second-generation cephalosporins (cefoxitin)
- Third-generation cephalosporins (ceftriaxone) plus metronidazole
Treatment Duration
- Prophylaxis for high-risk wounds: 3-5 days 1, 2
- Uncomplicated infections: 7-10 days 2
- Septic arthritis: 3-4 weeks 2
- Osteomyelitis: 4-6 weeks 2
Critical Pitfalls to Avoid
Never use these antibiotics alone for dog bites—they have poor activity against Pasteurella multocida: 2
- First-generation cephalosporins (e.g., cephalexin)
- Macrolides (e.g., azithromycin)
- Penicillinase-resistant penicillins (e.g., dicloxacillin)
Note that older literature from 1980 incorrectly recommended these agents; current guidelines explicitly contraindicate them. 6, 2
Special consideration for asplenic patients or those with liver disease: Be particularly vigilant for Capnocytophaga canimorsus, which can cause severe sepsis in these populations. 1, 2
Additional Wound Management
Beyond antibiotics, ensure: 1, 2, 3
- Thorough wound cleansing with sterile normal saline (avoid high-pressure irrigation which spreads bacteria deeper)
- Debridement of necrotic tissue
- Tetanus prophylaxis if vaccination not current
- Rabies prophylaxis consideration with local health official consultation
Evidence Context
The infection rate for dog bites is relatively low at 5-25%, compared to 30-50% for cat bites. 1, 2 A meta-analysis showed that prophylactic antibiotics reduce infection risk (relative risk 0.56), with a number needed to treat of 14 patients to prevent one infection. 7 However, the most recent consensus guidelines emphasize selective use based on risk stratification rather than universal prophylaxis, balancing infection prevention against antimicrobial stewardship. 1, 2