What is the recommended antibiotic regimen for a patient with a dog bite, considering potential allergies and underlying medical conditions?

Dog Bite Antibiotic Management

First-Line Antibiotic Choice

Amoxicillin-clavulanate 875/125 mg twice daily is the preferred oral antibiotic for dog bite wounds when antibiotics are indicated. 1, 2, 3

This combination provides comprehensive coverage against the polymicrobial flora typical in dog bites, including Pasteurella multocida (present in 50% of dog bites), Staphylococcus aureus, Streptococcus species, and anaerobes such as Bacteroides, Fusobacterium, Porphyromonas, and Prevotella species. 1, 2

When to Prescribe Antibiotics: Risk Stratification

Antibiotics should NOT be prescribed if the patient presents ≥24 hours after the bite without signs of infection, as prophylactic antibiotics are only beneficial when given early (within 24 hours) for fresh wounds at high risk. 2

High-Risk Wounds Requiring Prophylaxis (if presenting <24 hours):

Wound location criteria:

• Hand, foot, face, or genital wounds 2
• Wounds near joints or that may have penetrated periosteum or joint capsule 1, 2
• Puncture wounds 4, 3

Patient risk factors:

• Immunocompromised status 2
• Diabetes mellitus 2
• Advanced liver disease 2
• Asplenia (particularly concerning for Capnocytophaga canimorsus) 2
• Prosthetic joints or heart valves 2
• Pre-existing or resultant edema of the affected area 2

Alternative Antibiotic Options

For Penicillin Allergy:

Oral alternatives:

• Doxycycline 100 mg twice daily (excellent activity against Pasteurella multocida) 1, 2
• Moxifloxacin 400 mg daily as monotherapy (good anaerobic coverage) 1, 2
• Clindamycin 300-450 mg three times daily PLUS a fluoroquinolone (ciprofloxacin 500-750 mg twice daily or levofloxacin 750 mg daily) 1, 2

For Severe Infections Requiring IV Therapy:

Intravenous options:

• Ampicillin-sulbactam 1.5-3.0 g every 6-8 hours 1
• Piperacillin-tazobactam 3.37 g every 6-8 hours 1, 2
• Carbapenems (ertapenem 1 g daily, imipenem 1 g every 6-8 hours, or meropenem 1 g every 8 hours) 1, 2
• Ceftriaxone 1 g every 12 hours PLUS metronidazole 500 mg every 8 hours 1, 2
• Cefoxitin 1 g every 6-8 hours 1, 2

Treatment Duration

Standard duration:

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

For IV therapy: Initial IV treatment for 3-5 days for patients with systemic symptoms, moderate to severe infections, or high-risk wounds, then transition to oral therapy when clinically improved, afebrile, and local signs are improving. 2

Critical Pitfalls to Avoid

DO NOT use these antibiotics alone for dog bites:

• First-generation cephalosporins (cephalexin, cefazolin) 2
• Macrolides (erythromycin, azithromycin) 2
• Penicillinase-resistant penicillins (dicloxacillin, nafcillin) 2

These agents have poor activity against Pasteurella multocida, which is present in 50% of dog bite wounds. 2

Special consideration: In asplenic patients or those with liver disease, maintain high suspicion for Capnocytophaga canimorsus infection, which can cause severe sepsis. 2

Essential Adjunctive Management

Wound care:

• Copiously irrigate with sterile normal saline using a 20-mL or larger syringe 4
• Explore for tendon, bone, or joint involvement and foreign bodies 2, 4
• Debride necrotic tissue 2

Tetanus prophylaxis: Update if not current within 10 years (Tdap preferred over Td if not previously given). 2

Rabies prophylaxis: Consult local health officials to determine need for postexposure prophylaxis (immune globulin plus vaccination on days 0,3,7, and 14). 2, 4