A 28-year-old woman presents to the emergency department with acute appendicitis confirmed on CT imaging. She is haemodynamically stable, afebrile, and has no signs of perforation. What is the drug of choice for initial antibiotic therapy?

Explanation

## Antibiotic Therapy in Acute Appendicitis **Key Point:** Acute appendicitis requires broad-spectrum coverage against gram-negative aerobes and anaerobes. The combination of a third-generation cephalosporin with metronidazole is the gold standard for uncomplicated appendicitis. ### Rationale for Ceftriaxone + Metronidazole 1. **Spectrum Coverage** - Ceftriaxone covers gram-negative aerobes (E. coli, Klebsiella, Proteus) - Metronidazole covers anaerobes (Bacteroides, Peptostreptococcus, Clostridium) - Combined regimen covers the polymicrobial flora of the appendix 2. **Dosing in Acute Appendicitis** - Ceftriaxone: 1–2 g IV every 12 hours - Metronidazole: 500 mg IV every 8 hours **High-Yield:** The appendix contains both aerobic and anaerobic bacteria; monotherapy is inadequate. Dual coverage is mandatory even in uncomplicated cases to prevent surgical site infections and sepsis. **Clinical Pearl:** In penicillin-allergic patients, fluoroquinolone (ciprofloxacin) + metronidazole is an acceptable alternative, but the cephalosporin combination remains first-line due to superior beta-lactamase inhibition. ### Alternative Regimens | Scenario | First-Line | Alternative | | --- | --- | --- | | Uncomplicated appendicitis | Ceftriaxone + metronidazole | Cefoxitin (single agent) | | Perforated appendicitis | Ceftriaxone + metronidazole ± gentamicin | Piperacillin-tazobactam | | Penicillin allergy | Fluoroquinolone + metronidazole | Clindamycin + gentamicin | **Warning:** Amoxicillin-clavulanate monotherapy is inadequate for appendicitis because it does not reliably cover all anaerobes and gram-negative organisms. Fluoroquinolone monotherapy lacks anaerobic coverage. Clindamycin alone is outdated and does not cover gram-negative aerobes.