Antibiotic Prophylaxis for Appendectomy
Based on the most recent and highest-quality guidelines, ceftriaxone (Option B) combined with metronidazole is the appropriate choice for appendectomy prophylaxis, though ceftriaxone alone is not ideal as it lacks adequate anaerobic coverage.
First-Line Prophylaxis Recommendations
The gold standard for appendectomy prophylaxis is cefazolin (a first-generation cephalosporin) combined with metronidazole for anaerobic coverage. 1 The 2024 WHO Essential Medicines guidelines specifically recommend cefazolin alone or in combination with metronidazole as first-line prophylaxis for GI surgery including appendectomy. 1
The Australian Therapeutic Guidelines (2019) explicitly state that for colorectal surgery including appendectomy, the first choice is cefazolin plus metronidazole, or alternatively cefoxitin as single therapy. 1
Analysis of the Given Options
Option A: Cephalexin
Cephalexin is NOT appropriate for appendectomy prophylaxis. Cephalexin is an oral first-generation cephalosporin used for outpatient infections, not for surgical prophylaxis which requires intravenous administration. 2 No guidelines support its use in this setting.
Option B: Ceftriaxone
Ceftriaxone can be used but is not optimal as monotherapy. 1 The 2020 WSES Jerusalem Guidelines note that for complicated appendicitis in children, ceftriaxone-metronidazole is an acceptable alternative combination. 1 However, the 2024 WHO guidelines specifically note that "ceftriaxone is often inappropriately used as first-line option in many LMICs and did not prioritize it." 1
Research evidence shows ceftriaxone has been studied for appendectomy prophylaxis with reasonable efficacy (6.1-11.1% infection rates), though it should be combined with metronidazole for anaerobic coverage. 3, 4
Option C: Metronidazole
Metronidazole alone is inadequate. While metronidazole provides excellent anaerobic coverage, it lacks activity against gram-negative aerobes (E. coli, Enterobacteriaceae) and staphylococci that commonly cause surgical site infections. 1 It must be combined with a cephalosporin or other beta-lactam.
Option D: Vancomycin
Vancomycin is NOT indicated for routine appendectomy prophylaxis. 1 Vancomycin is reserved for specific situations: documented beta-lactam allergy, known MRSA colonization, or reoperation in units with high MRSA prevalence. 1
Optimal Prophylaxis Protocol
For uncomplicated appendicitis:
- Single preoperative dose of broad-spectrum antibiotics (cefazolin 2g IV or cefazolin + metronidazole) given 0-60 minutes before surgical incision 1
- No postoperative antibiotics needed 1
For complicated appendicitis (perforation, abscess):
- Preoperative cefazolin + metronidazole or broader-spectrum coverage 1
- Postoperative antibiotics for 24 hours to 3-5 days maximum with adequate source control 1
- Extended-spectrum antibiotics (piperacillin-tazobactam, ceftriaxone-metronidazole) for perforated cases 1
Critical Pitfalls to Avoid
- Never use oral antibiotics (like cephalexin) for surgical prophylaxis—IV administration is mandatory 2
- Never use monotherapy with metronidazole or vancomycin for routine prophylaxis 1
- Avoid prolonging antibiotics beyond 3-5 days in complicated cases with adequate source control 1
- Do not use third-generation cephalosporins as first-line when first-generation options are available, to preserve antimicrobial stewardship 1, 2
Answer: B (Ceftriaxone) is the only acceptable option from the list provided, though it should ideally be combined with metronidazole and is not the preferred first-line agent.