In a patient with unknown tetanus immunization status and possible penicillin allergy who sustains a deep cat bite to the hand, how should the wound be managed, including irrigation, tetanus prophylaxis, antibiotic selection, and rabies post‑exposure prophylaxis?

Cat Bite Treatment: Evidence-Based Management Protocol

Immediate Wound Management

All cat bite wounds—especially deep punctures to the hand—require immediate copious irrigation with sterile normal saline for approximately 15 minutes, followed by povidone-iodine solution, as this is the single most effective intervention to reduce infection risk and potential rabies transmission. 1, 2

Wound Care Essentials

• Cleanse thoroughly with soap and water for 15 minutes, then irrigate with sterile normal saline—no need for antibiotic-containing solutions 1
• Apply povidone-iodine or similar virucidal agent after initial cleansing to further reduce bacterial and viral load 2
• Examine carefully for tendon involvement, bone penetration, or joint capsule violation—pain disproportionate to injury near a joint suggests periosteal penetration 1
• Do NOT close the wound with sutures, as infected wounds should never be closed and cat bites carry extremely high infection rates (20-80%) 1, 3
• Elevate the injured hand using a sling to accelerate healing and reduce swelling 1

Critical pitfall: Hand wounds from cat bites are particularly dangerous and often more serious than wounds to other body parts due to deep inoculation of bacteria into tendon sheaths and joint spaces 1, 4

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Antibiotic Selection for Penicillin Allergy

For patients with penicillin allergy, use either doxycycline PLUS metronidazole, OR a fluoroquinolone (such as levofloxacin or moxifloxacin) PLUS clindamycin to cover both aerobic and anaerobic pathogens including Pasteurella multocida. 1

Antibiotic Regimen Details

First-line (if no penicillin allergy):

• Amoxicillin-clavulanate 875/125 mg twice daily for 7-10 days 1, 5

For penicillin-allergic patients:

• Doxycycline 100 mg twice daily PLUS metronidazole, OR 1
• Fluoroquinolone (levofloxacin or moxifloxacin) PLUS clindamycin 300-450 mg three times daily 1

Rationale: Cat bites harbor an average of 5 different aerobic and anaerobic organisms per wound, with Pasteurella multocida present in over 90% of cat oral cavities and isolated in >50% of infected cat bite wounds 1, 3, 5. Anaerobes including Fusobacterium, Bacteroides, and Porphyromonas species produce β-lactamases, making penicillin and first-generation cephalosporins inadequate 1

Duration: 7-10 days for uncomplicated wounds; 3-4 weeks for septic arthritis; 4-6 weeks for osteomyelitis 1

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Tetanus Prophylaxis for Unknown Immunization Status

Administer tetanus toxoid 0.5 mL intramuscularly immediately if tetanus status is unknown or if >10 years have elapsed since the last dose; use Tdap (tetanus-diphtheria-pertussis) if the patient has never received it. 1, 2

• Give tetanus toxoid for any patient with unknown or incomplete primary series 1
• For "dirty wounds" (which cat bites are), give booster if >5 years since last dose 1
• Tdap is preferred over Td if not previously administered 1

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Rabies Post-Exposure Prophylaxis Algorithm

Step 1: Assess Cat Status

If the cat is healthy, domestic, and available for observation:

• Confine and observe the cat for 10 days without initiating prophylaxis 6, 2
• If the cat remains healthy for the full 10 days, no rabies prophylaxis is needed as it was not shedding virus at the time of bite 6, 2

Initiate immediate rabies post-exposure prophylaxis if:

• Cat is stray, feral, or unwanted 2
• Cat cannot be confined for 10-day observation 2
• Cat dies or develops illness before completing observation 2
• Cat shows signs of rabies during observation 2
• Attack was unprovoked (unprovoked attacks are more likely to indicate rabies) 6, 2

Step 2: Rabies Prophylaxis Regimen (for Previously Unvaccinated Patients)

Administer Human Rabies Immune Globulin (HRIG) 20 IU/kg body weight on day 0:

• Infiltrate up to half the dose into and around the wound if anatomically feasible 6, 7
• Inject the remainder intramuscularly in the gluteal region 6, 7
• HRIG may be given up to day 7 after first vaccine dose if not initially administered; after day 7, HRIG is contraindicated as vaccine-induced antibodies are presumed present 6, 7

Administer rabies vaccine series:

• Give 4-5 doses on days 0,3,7,14, and 28 6, 2
• Inject in the deltoid (adults) or anterolateral thigh (children)—never in the gluteal area as this produces lower antibody titers 7

Critical pitfall: Never exceed the 20 IU/kg HRIG dose, as excess can suppress active antibody production 6, 7, 2

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Follow-Up and Monitoring

• Reassess within 24 hours by phone or office visit 1
• Hospitalize if infection progresses despite appropriate antibiotics and wound care 1
• Consider a single initial parenteral antibiotic dose before starting oral therapy for deep hand wounds 1
• Monitor for infectious complications: septic arthritis, osteomyelitis, subcutaneous abscess, tendonitis, or bacteremia 1, 2
• Watch for noninfectious complications: tendon/nerve injury, compartment syndrome, or fracture 1

Hand wounds require particularly close follow-up as they carry the greatest infection risk and potential for long-term disability if not managed aggressively 4, 5, 8