What is the recommended prophylactic antibiotic (including dose and duration) for a cat bite, and what alternatives should be used in patients with a true penicillin allergy?

Cat Bite Antibiotic Prophylaxis

First-Line Recommendation

Amoxicillin-clavulanate 875/125 mg orally twice daily for 3-5 days is the definitive prophylactic antibiotic for cat bites, providing optimal coverage against Pasteurella multocida and the polymicrobial flora characteristic of feline oral cavities. 1

Rationale for Amoxicillin-Clavulanate

• Cat bites carry a 20-80% infection risk, dramatically higher than the 3-18% risk from dog bites, making prophylaxis essential 2
• Pasteurella multocida is present in approximately 90% of feline oral cavities and is isolated in over half of all infected cat bite wounds 2, 3
• Amoxicillin-clavulanate provides comprehensive coverage against P. multocida, staphylococci, streptococci, and anaerobes—the typical polymicrobial mix in cat bites averaging 5 different organisms per wound 4
• Studies demonstrate 100% susceptibility of P. multocida to amoxicillin-clavulanate, confirming its continued efficacy 2

Indications Requiring Prophylaxis

Prophylactic antibiotics are mandatory for: 1

• Deep puncture wounds (cat teeth create narrow, deep wounds that seed bacteria into deep tissues)
• Hand, foot, face, or near-joint wounds (highest infection and complication risk)
• Wounds presenting >8-12 hours after injury
• Immunocompromised patients
• Any wound with early signs of infection

Alternatives for Penicillin Allergy

For Mild/Non-Severe Penicillin Allergies:

Doxycycline 100 mg orally twice daily for 3-5 days 4, 1

• Excellent P. multocida activity with 94% susceptibility 2
• Provides good coverage against staphylococci and anaerobes 4
• Some streptococci may be resistant, but this is acceptable given overall efficacy 4

For Severe Penicillin Allergies (Anaphylaxis History):

Option 1: Fluoroquinolone PLUS clindamycin 4, 1

• Ciprofloxacin 500-750 mg orally twice daily PLUS clindamycin 300 mg orally three times daily
• OR Levofloxacin 750 mg orally daily PLUS clindamycin 300 mg orally three times daily
• Fluoroquinolone covers P. multocida and gram-negatives; clindamycin covers anaerobes and gram-positives 4, 1

Option 2: Trimethoprim-sulfamethoxazole PLUS metronidazole 4

• TMP-SMZ 160-800 mg (one double-strength tablet) orally twice daily PLUS metronidazole 250-500 mg orally four times daily
• TMP-SMZ covers aerobes; metronidazole covers anaerobes 4

Critical Pitfalls to Avoid

Never use these as monotherapy for cat bites: 4, 1

• First-generation cephalosporins (cephalexin, cefazolin)—poor P. multocida activity
• Penicillinase-resistant penicillins (dicloxacillin)—inadequate P. multocida coverage
• Clindamycin alone—completely misses P. multocida
• Erythromycin—poor P. multocida activity
• Cefuroxime or ceftriaxone alone—inadequate anaerobic coverage despite good P. multocida activity 4

Duration of Therapy

• 3-5 days for uncomplicated prophylaxis in clean wounds 1
• 7-14 days if early infection signs are present (erythema, purulent drainage, lymphangitis) 1

When to Escalate to Intravenous Therapy

Switch to IV antibiotics if: 1

• Systemic signs develop (fever, rigors, hypotension)
• Deep tissue involvement or osteomyelitis suspected
• Immunocompromised patient with moderate-to-severe injury
• Failure of oral therapy after 48-72 hours

IV First-Line: Ampicillin-sulbactam 1.5-3.0 g IV every 6-8 hours 4, 1

IV for Penicillin Allergy: Carbapenem (ertapenem 1 g IV daily, meropenem 1 g IV every 8 hours, or imipenem 1 g IV every 6-8 hours) 4, 1

Essential Adjunctive Management

All cat bite wounds require: 1

• Copious irrigation with sterile normal saline under pressure
• Tetanus immunization update if >5 years since last dose
• Rabies risk assessment (consult local public health)
• Elevation of affected extremity to reduce swelling
• Avoid primary closure of puncture wounds—cat bites create deep, narrow tracts prone to abscess formation 1

Special Consideration: Hand Wounds

• Hand bites carry the highest infection and complication risk, including tenosynovitis, septic arthritis, and osteomyelitis 1, 5, 3
• Infection typically manifests within 12-24 hours as rapidly developing cellulitis with serosanguineous or purulent drainage 5
• Consider early surgical consultation for deep hand wounds, especially those near joints or tendons 1

Red Flags for Immediate Return

Instruct patients to return immediately for: 1

• Increasing pain, redness, or swelling
• Purulent drainage
• Fever or chills
• Decreased range of motion
• Red streaking (lymphangitis)