What is the recommended dose of cephalexin (cephalosporin) for an open fracture?

Cephalexin Dosing for Open Fractures

Cephalexin is NOT the recommended cephalosporin for open fracture management—you should use intravenous cefazolin instead, not oral cephalexin. 1

Why Cephalexin is Inappropriate

• Open fractures require immediate IV antibiotic therapy, not oral agents, because antibiotics must be started within 3 hours of injury to prevent infection, and IV administration ensures rapid, reliable tissue penetration. 1, 2

• Cephalexin is an oral first-generation cephalosporin indicated for outpatient infections like pharyngitis, skin infections, and uncomplicated cystitis—not for acute traumatic open fractures requiring surgical intervention. 3

• The standard of care for open fractures is IV cefazolin, which has been extensively studied and validated in trauma guidelines, whereas cephalexin has no established role in open fracture prophylaxis. 1, 4, 5

Correct Antibiotic Regimen for Open Fractures

For Gustilo-Anderson Type I and II Open Fractures:

• Administer cefazolin 2g IV initially, with re-injection of 1g if surgery duration exceeds 4 hours. 1

• Continue for 24 hours maximum after wound closure (operative period only). 1, 5

• Start antibiotics within 3 hours of injury—delays beyond this significantly increase infection risk. 1, 2

For Gustilo-Anderson Type III Open Fractures:

• Use cefazolin 2g IV plus an aminoglycoside (gentamicin 5 mg/kg/day) for enhanced gram-negative coverage. 1

• Continue for 48-72 hours post-injury but no more than 24 hours after wound closure. 1, 5

• Add aminopenicillin + beta-lactamase inhibitor (e.g., ampicillin-sulbactam) 2g IV if there is gross contamination, soil exposure, or farm-related injury to cover anaerobes including Clostridium species. 1

For Type III Fractures with Bone Loss:

• Add local antibiotic delivery systems (antibiotic-impregnated beads, gentamicin-coated implants) as adjuncts to systemic therapy. 4, 5

Critical Timing Considerations

• Administer the first dose within 60 minutes before surgical incision if the patient is going directly to the operating room. 1, 5

• If antibiotics are delayed beyond 3 hours from injury, infection risk increases substantially—this is a critical window that cannot be missed. 1, 2

Common Pitfalls to Avoid

• Never use oral antibiotics like cephalexin for acute open fracture management—IV administration is mandatory for adequate tissue penetration in traumatized limbs. 1

• Do not extend prophylaxis beyond 24 hours after wound closure unless there is documented infection—prolonged prophylaxis increases antibiotic resistance and adverse effects without reducing infection rates. 1, 5

• Do not use wound cultures obtained immediately post-injury to guide antibiotic selection—initial cultures do not correlate with infecting pathogens and should not direct prophylactic therapy. 2

• Do not forget to add penicillin for farm injuries or gross soil contamination—failure to cover anaerobes in these scenarios can lead to devastating clostridial infections. 1

Alternative Agents for Beta-Lactam Allergy

• Use clindamycin 900 mg IV plus gentamicin 5 mg/kg/day if the patient has a documented beta-lactam allergy. 1

• Vancomycin 30 mg/kg over 120 minutes is an alternative for severe beta-lactam allergies, but routine MRSA coverage is not recommended unless there are specific institutional epidemiologic concerns. 1, 5