What is the antibiotic of choice for open fractures?

Antibiotic of Choice for Open Fractures

For open fractures, cefazolin 2g IV is the antibiotic of choice, administered as soon as possible (ideally within 3 hours of injury), with treatment stratified by Gustilo-Anderson classification and limited to 24 hours after wound closure for most cases. 1, 2

First-Line Antibiotic Selection by Fracture Grade

Type I and II Open Fractures

• Cefazolin 2g IV slow is the recommended first-line agent, effectively targeting Staphylococcus aureus, streptococci, and aerobic gram-negative bacilli 1, 3, 2
• Reinject 1g if surgical duration exceeds 4 hours 4, 2
• Duration should be limited to the operative period with a maximum of 24 hours after initial injury 1, 2
• Extended-spectrum antibiotic coverage beyond gram-positive organisms does not decrease infectious complications, hospital length of stay, or mortality for these fracture grades 1

Type III Open Fractures

• Combination therapy is required: cefazolin 2g IV PLUS an aminoglycoside (gentamicin 5 mg/kg/day) to provide enhanced gram-negative coverage 1, 2
• However, recent Surgical Infection Society guidelines recommend against extended antimicrobial coverage beyond gram-positive organisms even for type III fractures, unless there is associated bone loss 1
• Duration should not exceed 24 hours after wound closure, but may extend up to 48-72 hours post-injury in the absence of clinical infection 1, 5

Critical Timing Considerations

• Antibiotics must be administered within 3 hours of injury—delays beyond this window significantly increase infection risk 1, 2, 5
• For surgical intervention, ensure administration within 60 minutes before incision 1, 2
• Recent pharmacokinetic data confirms that cefazolin achieves sustained concentrations above the MIC for S. aureus at open fracture sites, though delivery is slightly delayed compared to healthy tissue 6

Special Circumstances

Gross Contamination or Farm-Related Injuries

• Add penicillin to cover anaerobic organisms, including Clostridium species, even for lower-grade fractures when contamination risk is high 2, 5

Beta-Lactam Allergy

• Clindamycin 900mg IV slow is the recommended alternative 3, 2
• For severe beta-lactam allergies, vancomycin 30mg/kg over 120 minutes can be used 4, 3, 2
• For Type III fractures with beta-lactam allergy, combine clindamycin with gentamicin 2

Adjunctive Local Antibiotic Strategies

• Local antibiotic delivery systems (antibiotic-impregnated beads, gentamicin-coated implants) are beneficial adjuncts for Type III fractures with bone loss 1, 2
• Vancomycin powder and tobramycin-impregnated beads may also be beneficial as local strategies 1, 2

Dosing Adjustments

• Standard cefazolin dosing (2g IV) should be increased for patients weighing >120kg 2
• All dosing requires adjustment for renal impairment 1, 2

Common Pitfalls to Avoid

• Do not delay antibiotic administration beyond 3 hours post-injury—this significantly increases infection risk 1, 3, 2
• Do not add aminoglycosides for Type I or II fractures—they should be reserved for Type III open fractures 3
• Do not use antiseptics or soap additives for initial wound irrigation—they provide no benefit over simple saline solution 1, 3
• Do not use initial wound cultures to direct prophylactic antibiotic choice—infecting pathogens do not typically correlate to organisms initially cultured after injury 5
• Do not extend antibiotic prophylaxis beyond 24 hours after wound closure unless there is active infection 1, 2
• Routine MRSA coverage with vancomycin is not recommended unless there are specific institutional epidemiologic concerns 1

Alternative Regimen: Ceftriaxone

• Ceftriaxone is a safe and effective alternative that offers 24-hour dosing and single antibiotic coverage for grade 3 open fractures without increasing infectious complications 7
• This option provides resource efficiency advantages with broader coverage and decreased frequency of administration 7