What is the recommended antibiotic regimen for acute appendicitis?

Antibiotic Regimen for Acute Appendicitis

Direct Recommendation

For uncomplicated appendicitis undergoing surgery, give a single preoperative dose of piperacillin-tazobactam 3.375g IV (or cefotaxime 2g IV plus metronidazole 500mg IV) within 60 minutes before incision, with no postoperative antibiotics needed. 1, 2, 3

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Uncomplicated Appendicitis (Non-Perforated) - Surgical Management

Preoperative Prophylaxis

• A single dose of broad-spectrum antibiotics given 0-60 minutes before surgical incision is mandatory to reduce wound infections and intra-abdominal abscesses 1, 3

Preferred Antibiotic Regimens

• Piperacillin-tazobactam 3.375g IV is the preferred single-agent therapy due to simplicity and broad aerobic/anaerobic coverage 2, 4
• Alternative single agents include ertapenem 1g IV every 24 hours 2, 3
• Combination therapy: cefotaxime 2g IV every 8 hours PLUS metronidazole 500mg IV every 6 hours 2

Postoperative Management

• No postoperative antibiotics are recommended for uncomplicated appendicitis - this is a strong recommendation with high-quality evidence 1, 3

Critical Pitfall

• Do NOT use ampicillin-sulbactam due to E. coli resistance rates exceeding 20% 2, 3
• Avoid cefotetan and clindamycin due to increasing Bacteroides fragilis resistance 2, 3
• Avoid aminoglycosides for routine prophylaxis in adults due to toxicity 2, 3

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Complicated Appendicitis (Perforated/Abscess) - Surgical Management

Antibiotic Selection

• Imipenem-cilastatin 1g IV every 8 hours or meropenem 1g IV every 8 hours for broader coverage in perforated appendicitis 2
• Piperacillin-tazobactam 4.5g IV every 6 hours is also appropriate for complicated cases 4

Duration of Therapy

• If complete source control is achieved surgically, discontinue antibiotics after 24 hours postoperatively 1, 2
• Maximum duration is 3-5 days postoperatively, even without complete source control - do not exceed this 1, 3
• This represents a significant departure from older practices of 7-10 day courses 1

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Pediatric Patients

Uncomplicated Appendicitis

• Single preoperative dose of cefoxitin or cefotetan (second- or third-generation cephalosporin) 2, 3
• No postoperative antibiotics are needed 1, 3

Complicated Appendicitis in Children

• Switch to oral antibiotics after 48 hours of IV therapy 1, 3
• Total antibiotic duration should be less than 7 days postoperatively 1, 3
• This early oral switch is safe and reduces hospital length of stay 1

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Non-Operative Management (Antibiotics-First Approach)

Patient Selection Criteria

• CT-confirmed uncomplicated appendicitis WITHOUT appendicolith 2, 5
• Appendicolith presence predicts 40-60% failure rate of antibiotic therapy 2, 5
• Appendiceal diameter ≥13mm, mass effect, or appendicolith on CT are high-risk features for antibiotic failure 5

Antibiotic Regimen

• Minimum 48 hours IV antibiotics followed by oral antibiotics for total 7-10 days 2
• IV options: piperacillin-tazobactam monotherapy OR combination therapy with cephalosporins/fluoroquinolones plus metronidazole 5, 6
• Specific regimen from population-based study: IV piperacillin-tazobactam followed by 9 days oral ciprofloxacin plus metronidazole 6

Expected Outcomes

• Success rate approximately 70-78% at 1 month, declining to 63-73% at 1 year 5, 7
• Recurrence rate at 5 years is 39% - patients must be counseled about this 2
• Fewer immediate complications than surgery, but higher long-term failure rate 7

When to Avoid Non-Operative Management

• Presence of appendicolith on imaging 2, 5
• Appendiceal diameter >13mm 5
• Mass effect on CT 5
• Patient unfit for delayed surgery if antibiotics fail 5

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Critically Ill or Healthcare-Associated Infections

Broad-Spectrum Coverage

• Meropenem 1g IV every 8 hours for high-severity or healthcare-associated infections 2
• Add vancomycin 25-30mg/kg loading dose if MRSA risk is present 2
• Consider echinocandin if high risk for invasive candidiasis 2

Important Caveats

• Do NOT routinely cover Enterococcus in community-acquired appendicitis 3
• Do NOT provide empiric antifungal coverage for Candida in routine cases 3
• Avoid quinolones unless local E. coli susceptibility is ≥90% 3

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Key Algorithmic Approach

1. Determine if uncomplicated vs complicated (based on CT findings and intraoperative assessment)
2. For uncomplicated + surgery: Single preoperative dose only, no postoperative antibiotics 1, 3
3. For complicated + adequate source control: Maximum 24 hours postoperatively 1, 2
4. For complicated + inadequate source control: Maximum 3-5 days postoperatively 1, 3
5. For non-operative management: Ensure no appendicolith, counsel about 39% 5-year recurrence, use 7-10 day course 2, 5