In a patient with a dog bite to the hand 5 days ago and no drug allergies, what antibiotic regimen and tetanus prophylaxis should be prescribed?

Dog Bite to Hand - 5 Days Post-Injury: Antibiotic and Tetanus Management

For a 5-day-old dog bite to the hand, prescribe amoxicillin-clavulanate 875/125 mg twice daily for 7-10 days, and administer tetanus prophylaxis (Tdap preferred if not previously given, or Td if last dose was >5 years ago). 1

Antibiotic Selection and Rationale

The hand is a high-risk location for dog bite infections due to limited soft tissue coverage, proximity to joints, tendons, and bones, and the presence of multiple tissue planes where infection can spread rapidly. At 5 days post-injury, this wound is already in the established infection timeframe (patients typically present after 8-12 hours with infection).

First-Line Treatment

• Amoxicillin-clavulanate 875/125 mg orally twice daily is the definitive first-line choice 1, 2
• Duration: 7-10 days 1
• This covers the polymicrobial flora typical of dog bites:
  • Pasteurella multocida (present in 50% of dog bites)
  • Staphylococci and streptococci (40% of cases)
  • Anaerobes including Bacteroides, Fusobacterium, and Prevotella species
  • Aerobic gram-negative rods

Critical Pitfall to Avoid

Do NOT use first-generation cephalosporins (cephalexin), penicillinase-resistant penicillins (dicloxacillin), macrolides (erythromycin), or clindamycin monotherapy—these have poor activity against P. multocida and should be avoided 3. This is a common prescribing error that can lead to treatment failure.

Alternative Regimens (if patient develops allergy)

Since you stated no allergies, these are not needed, but for completeness:

• Doxycycline 100 mg twice daily (excellent Pasteurella coverage) 1, 2
• Moxifloxacin 400 mg daily (monotherapy with anaerobic coverage) 1, 2
• Ciprofloxacin or levofloxacin plus metronidazole (if fluoroquinolone chosen, must add anaerobic coverage) 1

Tetanus Prophylaxis

Administer tetanus toxoid if the patient has not received vaccination within the past 5 years for this contaminated wound 1.

Specific Recommendations:

• Tdap (tetanus, diphtheria, pertussis) is preferred over Td if the patient has never received Tdap 1
• For "dirty wounds" (which dog bites are), give booster if >5 years since last dose 4
• For clean wounds, the interval is >10 years, but dog bites are NOT clean wounds
• If primary vaccination series incomplete or unknown: patient needs both tetanus toxoid AND tetanus immune globulin (TIG) 250 units IM at a separate site 4

Documentation Check

Verify the patient's tetanus history. If uncertain or incomplete primary series, assume they need full prophylaxis. Military service since 1941 suggests at least one dose received 4.

Additional Critical Management Points

Wound Assessment at 5 Days

At this timeframe, assess for:

• Signs of established infection: erythema, swelling, purulent drainage, warmth, lymphangitic streaking, fever 5
• Deep structure involvement: Check neurovascular status (pulses, sensation), range of motion of adjacent joints, tendon function 6, 7
• Systemic signs: Fever, malaise suggesting deeper infection or sepsis

When to Escalate Care

The patient needs immediate surgical evaluation if:

• Purulent drainage or abscess formation
• Joint space involvement (septic arthritis)
• Tenosynovitis (infection of tendon sheath)
• Osteomyelitis suspected
• Neurovascular compromise
• Systemic signs of sepsis
• Failure to improve on oral antibiotics within 48-72 hours

Hand infections from dog bites can progress rapidly to serious complications including permanent functional impairment.

Wound Closure Considerations

At 5 days post-injury, do NOT perform primary closure 1. The wound is contaminated and in the infection window. Hand bite wounds have higher infection rates when closed 1. The wound should be left open or approximated at most.

Rabies Consideration

While not explicitly asked, verify the dog's rabies vaccination status. If unknown or the dog cannot be observed, rabies postexposure prophylaxis may be indicated 6, 7, 8.

Evidence Strength

The recommendation for amoxicillin-clavulanate comes from the 2014 IDSA Guidelines (highest quality guideline evidence available), which provides strong recommendations based on moderate-quality evidence 1. While a meta-analysis showed only marginal benefit for prophylactic antibiotics in low-risk wounds, hand bites are explicitly high-risk and warrant treatment 1. The tetanus recommendations are based on ACIP guidelines and consistent across multiple authoritative sources 1, 4.

The combination of hand location + 5-day delay makes this a high-risk scenario requiring aggressive antibiotic therapy and close follow-up.