What antibiotics are used to treat acute appendicitis?

From the Guidelines

Antibiotics are a crucial component in the management of acute appendicitis, and the most recent evidence suggests that a single preoperative dose of broad-spectrum antibiotics is sufficient for uncomplicated cases, while complicated cases may require extended antibiotic therapy. For uncomplicated appendicitis, a combination of cefazolin (1-2g IV every 8 hours) plus metronidazole (500mg IV every 8 hours) is typically recommended as first-line therapy 1. Alternatively, piperacillin-tazobactam (3.375g IV every 6 hours) or ertapenem (1g IV daily) can be used as single-agent therapy. For patients with penicillin allergies, ciprofloxacin (400mg IV every 12 hours) plus metronidazole is an appropriate alternative. These antibiotics should be administered preoperatively and continued for 24 hours after appendectomy for uncomplicated cases. For complicated appendicitis (with perforation, abscess, or peritonitis), antibiotic therapy should be extended to 3-5 days, with transition to oral antibiotics once the patient shows clinical improvement, as evidenced by the 2020 update of the WSES Jerusalem guidelines 1. Common oral regimens include amoxicillin-clavulanate (875/125mg twice daily) or ciprofloxacin (500mg twice daily) plus metronidazole (500mg three times daily). The use of antibiotics in acute appendicitis is supported by high-quality evidence, including a recent meta-analysis and randomized controlled trials 1. It is essential to note that the optimal duration of antibiotic therapy remains a topic of debate, but current evidence suggests that shorter courses of antibiotics (3-5 days) are sufficient for complicated appendicitis with adequate source control 1. In summary, antibiotics play a vital role in the management of acute appendicitis, and the choice and duration of antibiotic therapy should be guided by the severity of the disease and the presence of complications.

From the FDA Drug Label

In patients treated for IAI (primarily patients with perforated or complicated appendicitis), the clinical success rates were 83.7% (36/43) for ertapenem and 63.6% (7/11) for ticarcillin/clavulanate in the EPP analysis. The antibiotic ertapenem can be used to treat acute appendicitis, with a clinical success rate of 83.7% in patients with complicated intra-abdominal infections (IAI), primarily those with perforated or complicated appendicitis 2.

• The clinical success rate for ertapenem is higher compared to ticarcillin/clavulanate (63.6%) in the treatment of IAI.
• Ertapenem may be considered as an option for the treatment of acute appendicitis, especially in cases of complicated appendicitis.

From the Research

Antibiotics for Acute Appendicitis

• The use of antibiotics for acute appendicitis has been studied in several research papers 3, 4, 5, with some suggesting that broad-spectrum antibiotics can successfully treat uncomplicated acute appendicitis in approximately 70% of patients.
• A study published in JAMA found that specific imaging findings on computed tomography (CT) can identify patients for whom an antibiotics-first management strategy is more likely to fail 3.
• Another study published in Prescrire international found that antibiotic therapy had fewer immediate complications than surgery, but more subsequent failures 4.
• A population-based study published in the World Journal of Surgery found that primary antibiotic treatment had fewer complications compared to primary surgery, and that antibiotic treatment can be offered as the first-line therapy to a majority of unselected patients with acute appendicitis 5.

Treatment Outcomes

• A study published in the International Journal of Antimicrobial Agents found that simplification of first-line antibacterial regimen for complicated appendicitis in children was associated with better adherence to guidelines and reduced use of antibiotics 6.
• The study also found that post-operative complications and duration of hospital stay were similar between the two treatment groups 6.
• A review published in the American Family Physician found that appendectomy via open laparotomy or laparoscopy is the standard treatment for acute appendicitis, but that intravenous antibiotics may be considered first-line therapy in selected patients 7.

Patient Selection

• The JAMA study found that CT findings of appendicolith, mass effect, and a dilated appendix greater than 13 mm are associated with higher risk of treatment failure of an antibiotics-first approach 3.
• The study suggests that surgical management should be recommended in patients with these high-risk CT findings who are fit for surgery 3.
• The Prescrire international study found that some patients may choose antibiotic therapy over surgery when informed of the risks and benefits 4.