What is the appropriate treatment for a patient presenting with a rat bite?

Rat Bite Treatment

For rat bites, immediately irrigate the wound thoroughly with copious sterile saline or water, provide tetanus prophylaxis if needed, and reserve antibiotics primarily for infected wounds or high-risk situations (hand/joint involvement), as the natural infection rate is only 2% and most wounds heal with conservative management alone. 1, 2

Immediate Wound Management

• Irrigate the wound immediately and thoroughly with sterile normal saline or running tap water to remove debris and reduce bacterial load—this is the cornerstone of treatment and takes priority over antibiotic administration 1
• Avoid using iodine- or antibiotic-containing solutions for routine cleansing, as they provide no benefit over water or saline 3, 1
• Remove only superficial debris; avoid aggressive debridement that causes additional tissue damage 3, 1
• Do not close infected wounds or wounds presenting >8 hours after injury; for clean, early-presenting wounds, consider approximation with Steri-Strips rather than sutures 3, 1
• Facial wounds are an exception and may be closed primarily after meticulous irrigation and prophylactic antibiotics 1

Antibiotic Decision Algorithm

When to AVOID Prophylactic Antibiotics (Most Cases)

• The natural infection rate for uninfected rat bites is only 2%, so prophylactic antibiotics are generally unnecessary 2
• Most rat bites can be managed with conservative wound care alone, without hospital admission or antibiotics 4
• Superficial scratches (Type I wounds) and uncomplicated bites without signs of infection require only wound care 4

When to USE Antibiotics

High-risk wounds requiring prophylaxis or treatment: 1

• Hand wounds or wounds near joints/bones (risk of septic arthritis or osteomyelitis)
• Puncture wounds with crush injury or devitalized tissue
• Wounds presenting >8 hours after injury
• Immunocompromised patients or those with significant comorbidities
• Any signs of established infection (redness, swelling, purulence, fever)

Antibiotic Selection

First-line oral therapy: 5, 1, 6

• Amoxicillin-clavulanate 875/125 mg twice daily (provides coverage for typical wound pathogens including Streptobacillus moniliformis, the causative agent of rat bite fever, plus anaerobes)

Alternative oral options for penicillin allergy: 5, 1

• Doxycycline 100 mg twice daily
• Fluoroquinolones (ciprofloxacin, levofloxacin, moxifloxacin) plus metronidazole
• Penicillin VK plus dicloxacillin

Intravenous therapy for severe infections: 5, 1

• Ampicillin-sulbactam 1.5-3.0 g every 6-8 hours (first-line)
• Piperacillin-tazobactam 3.37 g every 6-8 hours
• Second-generation cephalosporins (cefoxitin)
• Carbapenems (ertapenem, imipenem, meropenem)

Duration of therapy: 1

• Standard wound infections: 7-10 days
• Septic arthritis: 3-4 weeks
• Osteomyelitis: 4-6 weeks

Tetanus Prophylaxis

• Tetanus prophylaxis is mandatory for all rat bites 1, 2
• Administer tetanus toxoid 0.5 mL intramuscularly if vaccination status is outdated or unknown 1
• Give booster if >5 years since last dose for dirty wounds or >10 years for clean wounds 1

Rabies Prophylaxis

• Rabies prophylaxis is generally NOT required for domestic rat bites in the United States, as small rodents are rarely infected with rabies 1
• Consult local health departments for regional risk assessment 1
• Consider prophylaxis only for feral or wild rodent bites in high-prevalence areas 1

Surgical Management by Wound Type

Based on wound classification: 4

• Type I (superficial scratches): Conservative wound care only, no surgery needed
• Type II (deeper bites with infection/ulceration): May require urgent drainage and debridement if infected
• Type III (full-thickness with tissue loss): May require skin grafting or reconstruction

Follow-Up and Warning Signs

• Elevate the injured extremity to reduce swelling and accelerate healing 1
• Follow up within 24 hours by phone or office visit for all patients 1
• Immediate re-evaluation required for: redness, swelling, foul-smelling drainage, increased pain, or fever 3
• Hospitalize if infection progresses despite appropriate antimicrobial therapy, deep tissue involvement is suspected, or patient is immunocompromised 1

Critical Pitfalls to Avoid

• Do not routinely prescribe prophylactic antibiotics for low-risk rat bites—the 2% infection rate does not justify universal prophylaxis 2
• Do not use first-generation cephalosporins or clindamycin monotherapy alone, as they have poor activity against Pasteurella and other bite pathogens 3
• Do not close wounds >8 hours old or any infected wounds 1
• Do not forget tetanus prophylaxis—most rat bite patients are deficient 2
• Be aware of rat bite fever (Streptobacillus moniliformis), which can present with fever, rash, and polyarthritis up to 2 weeks after the bite, and may occur even without fever 6, 7