What oral antibiotic should I prescribe for a patient with a dog‑scratch wound who has no penicillin allergy and normal renal and hepatic function?

Antibiotic Treatment for Dog Scratch Wounds

For a patient with a dog scratch wound and no penicillin allergy, prescribe amoxicillin-clavulanate 875/125 mg twice daily orally as first-line therapy. 1, 2

First-Line Antibiotic Choice

• Amoxicillin-clavulanate is the definitive first-line treatment for dog bite and scratch wounds, providing comprehensive coverage against the polymicrobial flora typically present in these injuries 1, 2
• The standard adult dose is 875/125 mg twice daily orally 1, 2
• This agent covers the key pathogens: Pasteurella multocida (present in 50% of dog wounds), Staphylococcus aureus (40%), streptococci, and anaerobes 1

Treatment Duration Algorithm

Base duration on wound characteristics and risk factors:

• 3-5 days for preemptive therapy in high-risk wounds (immunocompromised patients, asplenic, advanced liver disease, hand/face injuries, wounds presenting >9 hours after injury, or injuries potentially penetrating periosteum/joint capsule) 1
• 7-10 days for uncomplicated soft tissue infections that are already clinically infected 2
• 3-4 weeks total for septic arthritis 2
• 4-6 weeks total for osteomyelitis 2

Critical Microbiology Considerations

Dog scratch and bite wounds are polymicrobial, containing an average of 5 different bacterial species 1, 2:

• Pasteurella multocida is the most critical pathogen, causing rapidly developing cellulitis within 12-24 hours 3
• Mixed aerobic and anaerobic organisms are present in 60% of wounds 2
• Capnocytophaga canimorsus poses particular risk in asplenic or liver disease patients, causing fulminant sepsis 2

Alternative Options (If Amoxicillin-Clavulanate Unavailable)

For non-anaphylactic penicillin allergy:

• Doxycycline 100 mg twice daily provides excellent activity against Pasteurella multocida 4, 1
• Note: Avoid in children under 8 years 1

For severe penicillin allergy, use combination therapy:

• Fluoroquinolone (moxifloxacin 400 mg daily, levofloxacin 500-750 mg daily, or ciprofloxacin 500-750 mg twice daily) PLUS metronidazole or clindamycin 300 mg three times daily for anaerobic coverage 4, 1, 2

Essential Adjunctive Management

Beyond antibiotics, ensure comprehensive wound care 1, 2:

• Thorough irrigation with copious sterile normal saline 1
• Tetanus prophylaxis if not vaccinated within past 10 years 1
• Rabies consultation with local health officials 1
• Avoid primary closure of puncture wounds or high-risk wounds (except facial wounds) 1

Critical Pitfalls to Avoid

Never use these agents as monotherapy for dog scratches/bites:

• First-generation cephalosporins (e.g., cephalexin) 1, 2
• Macrolides (e.g., azithromycin, erythromycin) 1, 2
• Penicillinase-resistant penicillins alone (e.g., dicloxacillin) 1, 2
• Clindamycin alone 4

These agents have poor or no activity against Pasteurella multocida, the predominant pathogen in dog wounds 1, 2. This is the most common prescribing error in animal bite management.

High-Risk Features Requiring Aggressive Management

Heightened vigilance and potentially IV therapy for:

• Hand, foot, face, or genital location wounds 2
• Immunocompromised status, asplenia, or advanced liver disease 1, 2
• Wounds with potential tendon, bone, or joint involvement 2
• Presentation >9 hours after injury 1

For these high-risk scenarios requiring IV therapy, use ampicillin-sulbactam 1.5-3.0 g every 6-8 hours, piperacillin-tazobactam 3.37 g every 6-8 hours, or a carbapenem before transitioning to oral amoxicillin-clavulanate 4, 2.