What antibiotics are recommended for acute appendicitis and how often should they be administered?

From the Guidelines

For acute appendicitis, broad-spectrum antibiotics should be initiated promptly, typically with a combination of cefazolin (1-2g IV every 8 hours) plus metronidazole (500mg IV every 8 hours), or piperacillin-tazobactam (3.375g IV every 6 hours) as a single agent, as recommended by the most recent guidelines 1. The choice of antibiotics should target common pathogens in appendicitis, including Escherichia coli, Bacteroides fragilis, and other enteric bacteria.

• The duration of antibiotic therapy depends on the severity of the infection, with uncomplicated cases typically requiring a 24-hour course and complicated cases (perforated or gangrenous) requiring 3-7 days of treatment 1.
• Antibiotics should be started preoperatively and continued postoperatively, with the goal of achieving adequate source control and preventing postoperative infections 1.
• The use of broad-spectrum antibiotics, such as piperacillin-tazobactam or ceftriaxone plus metronidazole, is recommended for patients with complicated appendicitis, especially if complete source control has not been achieved 1.
• For patients with penicillin allergies, alternative regimens such as ciprofloxacin (400mg IV every 12 hours) plus metronidazole can be used 1.
• Therapy should be adjusted based on culture results when available, and can be switched to oral antibiotics once the patient shows clinical improvement with normal vital signs, white blood cell count, and resumed oral intake 1.

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. Ertapenem was evaluated in pediatric patients 3 months to 17 years of age in two randomized, multicenter clinical trials ... ertapenem (15 mg/kg intravenous (IV) every 12 hours in patients 3 months to 12 years of age, and 1 g IV once a day in patients 13 to 17 years of age)

The recommended antibiotic for acute appendicitis is ertapenem. The administration frequency is:

• 15 mg/kg IV every 12 hours in patients 3 months to 12 years of age
• 1 g IV once a day in patients 13 to 17 years of age 2

From the Research

Antibiotics for Acute Appendicitis

• The use of antibiotics for acute appendicitis has been studied in several trials, with varying results 3, 4, 5, 6, 7.
• The antibiotics used in these studies include amoxicillin + clavulanic acid, cefotaxime, fluoroquinolones, metronidazole, and tinidazole 3.
• The duration of antibiotic treatment varied from 7 to 15 days, with some studies using intravenous antibiotics followed by oral antibiotics 3, 7.
• The frequency of administration also varied, with some studies using once-daily dosing and others using multiple doses per day 4, 5.

Recommended Antibiotics and Dosage

• A study published in 2014 found that antibiotic therapy with amoxicillin + clavulanic acid, cefotaxime, or a fluoroquinolone, with or without metronidazole or tinidazole, was effective in treating acute appendicitis 3.
• Another study published in 2021 compared oral moxifloxacin with intravenous ertapenem followed by oral levofloxacin and metronidazole, and found that both regimens were effective in treating uncomplicated acute appendicitis 7.
• The dosage of antibiotics used in these studies varied, but typical dosages included:
  • Amoxicillin + clavulanic acid: 500-1000 mg every 8-12 hours 3
  • Cefotaxime: 1-2 g every 8-12 hours 3, 4
  • Fluoroquinolones: 400-500 mg every 24 hours 3, 7
  • Metronidazole: 500 mg every 8-12 hours 3, 5
  • Tinidazole: 500-1000 mg every 12-24 hours 3

Administration Frequency

• The frequency of antibiotic administration varied in the studies, but typical regimens included:
  • Once-daily dosing with oral moxifloxacin 7
  • Multiple doses per day with intravenous cefotaxime or ertapenem 4, 7
  • Twice-daily dosing with oral amoxicillin + clavulanic acid or fluoroquinolones 3