What is the recommended antibiotic regimen for a patient with appendicitis?

Antibiotic Regimen for Appendicitis

For uncomplicated appendicitis undergoing surgery, administer a single preoperative dose of cefotaxime 2g IV plus metronidazole 500mg IV, or piperacillin-tazobactam 3.375g IV as monotherapy, with no postoperative antibiotics needed if adequate source control is achieved. 1, 2

Uncomplicated (Non-Perforated) Appendicitis

Preoperative Prophylaxis

• Single dose 0-60 minutes before incision is sufficient for uncomplicated appendicitis 2
• Preferred regimens:
  • Piperacillin-tazobactam 3.375g IV every 6 hours (simplest single-agent option) 1, 3
  • Cefotaxime 2g IV every 8 hours PLUS metronidazole 500mg IV every 6 hours 1
  • Ertapenem 1g IV every 24 hours (alternative single-agent) 1, 4
  • Ticarcillin-clavulanate, cefoxitin, moxifloxacin, or tigecycline are also acceptable 2

Postoperative Management

• Discontinue antibiotics within 24 hours after appendectomy if adequate source control achieved 1, 2
• No postoperative antibiotics are needed for uncomplicated cases 5, 2

Complicated (Perforated/Abscess) Appendicitis

Antibiotic Selection

• Broader-spectrum coverage required for perforated appendicitis 5, 2
• Preferred regimens:
  • Imipenem-cilastatin 1g IV every 8 hours 1
  • Meropenem 1g IV every 8 hours 1
  • Piperacillin-tazobactam (higher dose for complicated cases) 5, 2
  • Ampicillin-sulbactam, ticarcillin-clavulanate, or doripenem 5

Duration of Therapy

• Limit to 3-5 days postoperatively even if complete source control not achieved 5, 1, 2
• 24 hours postoperatively is adequate if complete source control achieved 5, 1
• Fixed-duration therapy (approximately 4 days) has similar outcomes to longer courses (approximately 8 days) 5

Pediatric Patients

Non-Perforated Appendicitis

• Single dose of second- or third-generation cephalosporin (cefoxitin or cefotetan) is sufficient 5, 1, 2
• No postoperative antibiotics needed 5, 2

Complicated Appendicitis in Children

• Ampicillin, clindamycin (or metronidazole), and gentamicin is the most common combination 5
• Alternatives: ceftriaxone-metronidazole or ticarcillin-clavulanate plus gentamicin 5
• Early switch to oral antibiotics after 48 hours is safe and cost-effective 1, 2
• Total duration should be less than 7 days postoperatively 2

Critical Antibiotics to AVOID

These agents have unacceptably high resistance rates and should not be used: 5, 1, 2

• Ampicillin-sulbactam (>20% E. coli resistance) 5, 1, 2
• Cefotetan (increasing Bacteroides fragilis resistance) 5, 1, 2
• Clindamycin (increasing Bacteroides fragilis resistance) 5, 1, 2
• Aminoglycosides (toxicity with equally effective alternatives available) 5, 1, 2
• Fluoroquinolones (unless local E. coli susceptibility ≥90%) 2

Non-Operative Management (Antibiotics-First Approach)

Patient Selection

• CT-confirmed uncomplicated appendicitis WITHOUT appendicolith 1, 3
• Appendicolith presence predicts 40-60% failure rate 1, 3
• Appendiceal diameter ≥13mm or mass effect increases failure risk to approximately 40% 3

Antibiotic Regimen

• Minimum 48 hours IV followed by oral antibiotics for total of 7-10 days 1
• Use same regimens as for uncomplicated appendicitis (piperacillin-tazobactam or cefotaxime plus metronidazole) 1, 3
• Success rate approximately 70% at initial treatment 3
• Recurrence rate 39% at 5 years - patients must be counseled 1

Healthcare-Associated or High-Severity Infections

Critically Ill Patients

• Meropenem 1g IV every 8 hours for healthcare-associated infections 1
• Add vancomycin 25-30mg/kg loading dose if MRSA risk present 1
• Consider echinocandin if high risk for invasive candidiasis 1
• Empiric therapy should be driven by local microbiologic results 5

Key Principles to Avoid Treatment Failure

DO NOT:

• Routinely cover Enterococcus in community-acquired appendicitis 5, 2
• Provide empiric antifungal coverage for Candida 5, 2
• Continue antibiotics beyond 3-5 days postoperatively in complicated cases with adequate source control 5, 1, 2
• Delay antibiotic administration while awaiting imaging - start empiric therapy when appendicitis clinically suspected 1
• Use narrow-spectrum regimens (cephalosporins alone without anaerobic coverage) - appendicitis involves mixed aerobic-anaerobic flora 1

DO:

• Administer loading doses in critically ill patients, especially for hydrophilic agents like beta-lactams 5
• Consider extended or prolonged infusion for beta-lactam antibiotics to maximize time above MIC 5
• Tailor therapy when culture and susceptibility reports become available 5