What antibiotic regimen is recommended for a patient with a gunshot wound?

Antibiotic Management for Gunshot Wounds

Direct Recommendation

For gunshot wounds, initiate a first-generation cephalosporin (cefazolin) immediately, adding an aminoglycoside (gentamicin) for severe injuries or visible contamination, plus penicillin or metronidazole for anaerobic coverage if there is soil contamination or gastrointestinal tract involvement, and continue therapy for 48-72 hours. 1, 2

Classification and Rationale

• Gunshot wounds are classified as contaminated wounds (Class III) requiring therapeutic antibiotic dosing, not prophylactic dosing 1, 2
• The presence of tissue destruction, potential foreign body contamination, and environmental exposure creates high infection risk 1
• Antibiotic administration should begin as soon as possible, ideally within 3 hours of injury, as delays significantly increase infection risk 1, 3

Recommended Antibiotic Regimen

First-Line Therapy

• Cefazolin (first-generation cephalosporin) provides essential coverage against Staphylococcus aureus and streptococci, the most common pathogens in penetrating trauma 1, 2, 4

Additional Coverage Based on Injury Characteristics

For severe injuries or visible contamination:

• Add gentamicin (aminoglycoside) for gram-negative coverage 1, 2

For soil contamination or gastrointestinal tract involvement:

• Add penicillin for anaerobic coverage (particularly Clostridium species) 1, 4
• Alternatively, add metronidazole for anaerobic coverage if gastrointestinal tract is violated 5, 4

For abdominal gunshot wounds with bowel perforation:

• Use single-agent broad-spectrum therapy: piperacillin-tazobactam, or a carbapenem (ertapenem, meropenem) 5
• Alternative combination: ceftriaxone plus metronidazole 5

Duration of Therapy

• 48-72 hours for most gunshot wounds, particularly high-velocity injuries 2
• 3-5 days for wounds with significant contamination or delayed debridement 1
• 5 days for abdominal gunshot wounds with distal ileal or colonic injury 6
• Do not extend therapy beyond 5 days unless there is documented infection, as this increases antibiotic resistance risk without benefit 1

Evidence Supporting Narrow-Spectrum Approach

• Recent civilian trauma data demonstrates that narrow-spectrum regimens (cefazolin-based) are as effective as broad-spectrum regimens for preventing post-traumatic infections in gunshot wounds 7
• Broad-spectrum coverage was associated with increased hospital length of stay and higher rates of multidrug-resistant bacteria colonization without improving infection outcomes 7
• Historical data confirms that single-agent therapy with aerobic and anaerobic coverage is as effective as multi-agent regimens for abdominal gunshot wounds, while being less toxic and less expensive 6

Wound-Specific Modifications

Thoracic gunshot wounds with hemothorax:

• Use the standard cefazolin-based regimen for 48-72 hours 2
• The presence of hemothorax indicates pleural cavity contamination and potential chest tube placement, both increasing infection risk 2

Extremity and soft tissue wounds:

• Cefazolin alone is typically sufficient 4
• Extended gram-negative coverage is unlikely to be necessary for extremity trauma 4

Central nervous system involvement:

• Cefazolin-based regimen is appropriate 4
• Add metronidazole only if there is gross contamination 4

Critical Pitfalls to Avoid

• Do not use prophylactic dosing - these are contaminated wounds requiring therapeutic doses 1, 3
• Do not delay antibiotic initiation beyond 3 hours after injury recognition 1, 3
• Do not routinely use broad-spectrum antibiotics (fluoroquinolones, carbapenems) for simple extremity or thoracic gunshot wounds, as this promotes resistance without improving outcomes 7, 4
• Do not extend antibiotics beyond 72 hours for non-abdominal wounds or beyond 5 days for abdominal wounds unless infection is documented 1, 2
• Do not forget anaerobic coverage when soil contamination is present or gastrointestinal tract is violated 1, 4

Surgical Management Priority

• The most important therapy is prompt surgical debridement and wound care - antibiotics are adjunctive 5, 3
• Prompt surgical consultation is mandatory for any signs of systemic toxicity or suspicion of necrotizing infection 5