What antibiotics are recommended for acute appendicitis?

Antibiotic Therapy for Acute Appendicitis

For acute appendicitis, broad-spectrum antibiotics targeting enteric gram-negative organisms and anaerobes should be initiated promptly, with specific regimens based on whether the appendicitis is uncomplicated or complicated. 1

Antibiotic Selection Based on Appendicitis Classification

Uncomplicated Appendicitis

• First-line options:

  • Single agent:

    • Second/third-generation cephalosporins (cefoxitin or cefotetan) 1, 2
    • Ticarcillin-clavulanate 2
    • Ertapenem 2
    • Moxifloxacin 2

  • Combination therapy:

    • Metronidazole + cefazolin/cefuroxime/ceftriaxone/cefotaxime 2
    • Metronidazole + ciprofloxacin/levofloxacin 2

• Duration: Single preoperative dose if surgical management is chosen 1

• Note: Avoid ampicillin-sulbactam, cefotetan, or clindamycin due to high resistance rates among E. coli and Bacteroides fragilis 2

Complicated Appendicitis (Perforated/Abscess)

• First-line options:

  • Piperacillin-tazobactam 1, 3

  • Ampicillin-sulbactam 1

  • Ticarcillin-clavulanate 1

  • Imipenem-cilastatin 1

  • Triple therapy (especially for pediatric patients):

    • Ampicillin + clindamycin (or metronidazole) + gentamicin 1

  • Alternative combination:

    • Ceftriaxone + metronidazole 1
    • Ticarcillin-clavulanate + gentamicin 1

• Duration: 3-5 days total for adults with adequate source control 1

Special Considerations

Pediatric Patients

• Uncomplicated appendicitis: Single broad-spectrum antibiotic (second/third-generation cephalosporin) 1
• Complicated appendicitis: IV antibiotics effective against enteric gram-negative organisms and anaerobes 1
• Duration: Can switch to oral antibiotics after 48 hours, with total therapy <7 days 1
• Note: Extended-spectrum antibiotics offer no advantage over narrower-spectrum agents in children 1

Non-Operative Management

For selected patients with uncomplicated appendicitis choosing antibiotic therapy instead of surgery:

• Initial IV regimens:

  • Ertapenem followed by oral cefdinir + metronidazole 1
  • Amoxicillin/clavulanate 1.2-2.2g every 6 hours 1
  • Ceftriaxone 2g daily + metronidazole 500mg every 6 hours 1
  • Cefotaxime 2g every 8 hours + metronidazole 500mg every 6 hours 1

• For beta-lactam allergy:

  • Ciprofloxacin 400mg every 8 hours + metronidazole 500mg every 6 hours 1
  • Moxifloxacin 400mg daily 1

• Duration: Typically 7-10 days total (IV followed by oral) 1, 4, 5

Important Clinical Pearls

1. Timing is critical: Initiate antibiotics as soon as diagnosis is established, even before surgery 1, 2

2. Source control: With adequate surgical source control, prolonging antibiotics beyond 3-5 days postoperatively provides no additional benefit 1

3. Treatment failure risk: When using antibiotics as primary therapy for uncomplicated appendicitis, approximately 23-27% of patients may require subsequent appendectomy within 1 year 2, 4

4. Appendicolith caution: The presence of an appendicolith increases the risk of failure with non-operative management; surgery is recommended in these cases 1

5. Cost-effectiveness: Monotherapy with appropriate broad-spectrum antibiotics is both economical and effective for complicated appendicitis 6

6. Transition to oral therapy: Early switch to oral antibiotics (after 48 hours) is safe and cost-effective in complicated appendicitis 1

7. Avoid unnecessary broad coverage: Extended-spectrum antibiotics offer no advantage over narrower-spectrum agents in most cases of appendicitis 1

By following these evidence-based recommendations for antibiotic therapy in acute appendicitis, clinicians can optimize treatment outcomes while practicing good antimicrobial stewardship.