## Therapeutic Antibiotics in Perforated Appendicitis **Key Point:** In perforated appendicitis with peritonitis, the drug of choice is a combination of a broad-spectrum beta-lactam (ceftriaxone or cefotaxime) PLUS metronidazole to ensure coverage of both aerobic enteric flora and anaerobes, which are critical in intra-abdominal infections. ### Why Combination Therapy is Mandatory **High-Yield:** Perforated appendicitis releases mixed flora (aerobic gram-negative rods, gram-positive cocci, and obligate anaerobes). Monotherapy is inadequate: - **Cephalosporin alone:** Covers aerobes but has variable anaerobic activity - **Metronidazole alone:** Covers anaerobes but lacks gram-negative coverage - **Combination:** Synergistic coverage of the polymicrobial infection **Mnemonic:** **COMA** = **C**ephalosporin + **O**ther (metronidazole) = **M**andatory in **A**ppendix perforation. ### Therapeutic vs. Prophylactic Dosing | Aspect | Prophylactic (Uncomplicated) | Therapeutic (Perforated) | | --- | --- | --- | | Timing | Before skin incision | After diagnosis; continued post-op | | Ceftriaxone dose | 1–2 g IV single dose | 1–2 g IV Q 8–12 hrs × 7–10 days | | Metronidazole | Not routinely added | **Always added** (500 mg IV Q 6–8 hrs) | | Duration | Single dose (or re-dose if long surgery) | 7–10 days or until clinical improvement | **Clinical Pearl:** In perforated appendicitis, antibiotics are started immediately after diagnosis (at laparotomy) and continued for 7–10 days. The combination of ceftriaxone + metronidazole is the gold standard and is recommended by IDSA, ACCP, and ACS guidelines. ### Why Other Options Fail - **Gentamicin alone:** Aminoglycosides lack anaerobic coverage and are not used as monotherapy for intra-abdominal infections; they are sometimes added to anaerobic coverage in severe cases but are not first-line. - **Chloramphenicol:** Broad spectrum but rarely used today due to bone marrow toxicity and superior alternatives available. - **Trimethoprim-sulfamethoxazole:** Inadequate anaerobic coverage and not recommended for serious intra-abdominal infections. **Tip:** Always remember: **perforated appendicitis = polymicrobial = combination therapy**. Cephalosporin + metronidazole is the standard regimen taught in all surgical textbooks and is the most frequently tested combination in NEET PG. [cite:Bailey & Love's Short Practice of Surgery 27e Ch 68; IDSA Intra-Abdominal Infection Guidelines]
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.