Antibiotic Coverage for Dog Bites in Penicillin-Allergic Patients
For penicillin-allergic patients with dog bites, use doxycycline 100 mg twice daily PLUS either clindamycin 300 mg three times daily OR metronidazole 500 mg three times daily for 3-5 days. 1
Primary Recommended Regimen
Doxycycline 100 mg PO twice daily PLUS clindamycin 300 mg PO three times daily is the preferred combination for patients with documented penicillin allergy. 1 This regimen provides:
- Excellent coverage of Pasteurella multocida (present in 50% of dog bites) via doxycycline 2, 1
- Coverage of Staphylococci and Streptococci (found in ~40% of bites) via both agents 1
- Anaerobic coverage (present in ~60% of wounds including Bacteroides, Fusobacterium, Porphyromonas, and Prevotella species) via clindamycin 2, 1
Alternative Regimens for Penicillin Allergy
If doxycycline plus clindamycin is not suitable, use fluoroquinolone-based combinations: 2, 1
- Moxifloxacin 400 mg daily as monotherapy (provides both aerobic and anaerobic coverage) 2, 1
- Levofloxacin 750 mg daily PLUS metronidazole 500 mg three times daily 2, 1
- Ciprofloxacin 500-750 mg twice daily PLUS metronidazole 500 mg three times daily 2, 1
The fluoroquinolones provide good activity against P. multocida but require metronidazole for adequate anaerobic coverage (except moxifloxacin). 2
What NOT to Use
Avoid these regimens in penicillin-allergic patients: 1
- First-generation cephalosporins (poor P. multocida coverage) 1
- Macrolides (inadequate P. multocida coverage) 1
- Clindamycin monotherapy (misses P. multocida entirely) 2, 1
Duration of Therapy
- 3-5 days for prophylaxis/early treatment of uncomplicated wounds 1
- 7-10 days for established infection 1
- 3-6 weeks for complicated infections (septic arthritis, osteomyelitis) 1
High-Risk Features Requiring Treatment
Strongly consider preemptive antibiotics for: 1
- Immunocompromised status or asplenia 1
- Advanced liver disease 1
- Moderate to severe injuries, especially to hand or face 1
- Puncture wounds penetrating periosteum or joint capsule 1
- Preexisting or resultant edema of affected area 1
Prophylactic antibiotics reduce infection risk with a relative risk of 0.56 (95% CI 0.38-0.82), though approximately 14 patients need treatment to prevent one infection. 3
Critical Pitfalls to Avoid
The most common error is using clindamycin alone, which provides excellent coverage for staphylococci, streptococci, and anaerobes but completely misses P. multocida—the most important pathogen in dog bites. 2 This is why combination therapy is essential in penicillin-allergic patients.
Second-generation cephalosporins like cefuroxime have good P. multocida activity but miss anaerobes, making them inadequate monotherapy. 2
Additional Management
- Wound irrigation with sterile normal saline and debridement of superficial debris 1
- Tetanus prophylaxis if not vaccinated within 10 years 2
- Consider that less than 10% of patients with penicillin allergy labels are truly allergic when formally tested, so allergy verification may allow use of preferred beta-lactam regimens in future encounters 4, 5