What is the recommended antibiotic regimen for treating appendicitis?

Antibiotic Regimen for Appendicitis

A single preoperative dose of broad-spectrum antibiotics is recommended for uncomplicated appendicitis, while complicated appendicitis requires 3-5 days of postoperative antibiotics with adequate source control. 1

Antibiotic Recommendations by Type of Appendicitis

Uncomplicated Appendicitis

• Preoperative antibiotics: Single dose of broad-spectrum antibiotics 0-60 minutes before surgical incision 1
• Postoperative antibiotics: Not recommended if adequate source control achieved 1
• Rationale: Preoperative antibiotics significantly reduce wound infections and intra-abdominal abscesses without requiring additional postoperative coverage 1

Complicated Appendicitis (perforation, abscess, peritonitis)

• Preoperative antibiotics: Single dose of broad-spectrum antibiotics 0-60 minutes before surgical incision 1
• Postoperative antibiotics: 3-5 days of broad-spectrum antibiotics 1
• Duration: Continue until clinical signs resolve and laboratory parameters improve (WBC, CRP) 2
• Evidence: Short-course therapy (24h) may be as effective as extended therapy with shorter hospital stays 1

Recommended Antibiotic Choices

For Uncomplicated Appendicitis

• Second or third-generation cephalosporins (e.g., cefoxitin, cefotetan) 1
• Alternative: Single dose of metronidazole has shown significant reduction in postoperative infections 3

For Complicated Appendicitis

• Intravenous options:
  • Meropenem 1g every 8 hours 4
  • Piperacillin-tazobactam 1
  • Ampicillin-sulbactam 1
  • Ticarcillin-clavulanate 1
  • Ceftriaxone + metronidazole 5

Special Populations

Pediatric Patients

• Uncomplicated appendicitis: Single broad-spectrum antibiotic dose 1
• Complicated appendicitis: Antibiotics effective against enteric gram-negative organisms and anaerobes 1
• Common pathogens: E. coli (66%), Streptococcus anginosus (45%), Bacteroides fragilis (22%), Pseudomonas aeruginosa (17%) 5
• Duration: Similar to adults, 3-5 days with clinical improvement 1

Elderly Patients

• Uncomplicated appendicitis: Preoperative broad-spectrum antibiotics strongly recommended; postoperative antibiotics not recommended 1
• Complicated appendicitis: Postoperative broad-spectrum antibiotics recommended 1
• Rationale: Elderly patients may have higher risk of complications, but evidence specifically for this population is limited 1

Clinical Pearls and Pitfalls

• Key pitfall: Continuing antibiotics longer than necessary in uncomplicated cases increases antibiotic resistance risk without improving outcomes 1
• Important consideration: Local microbiology patterns and resistance rates should guide antibiotic selection 5
• Monitoring: Discontinue antibiotics based on clinical improvement (resolution of fever, normalization of WBC, declining CRP) rather than arbitrary time points 1
• Duration caution: Evidence shows fixed-duration therapy (3-5 days) has similar outcomes to longer courses that extend until complete resolution of physiological abnormalities 1

Emerging Evidence

Recent studies show that some cases of uncomplicated appendicitis may be treated with antibiotics alone without surgery, but appendectomy remains the standard treatment with lower long-term failure rates 6, 7. When antibiotics-only approach is used, intravenous antibiotics followed by oral therapy for a total of 8-15 days is typically employed 6.

The evidence strongly supports that a single preoperative dose of antibiotics followed by no postoperative antibiotics for uncomplicated appendicitis, and 3-5 days of postoperative antibiotics for complicated appendicitis, provides the optimal balance of infection prevention and antibiotic stewardship.