What antibiotics are used to treat abdominal infections (peritonitis)?

From the Guidelines

For abdominal infections, empiric antibiotic therapy should include a combination of agents to cover gram-negative bacteria, gram-positive bacteria, and anaerobes, with piperacillin-tazobactam 3.375g IV every 6 hours or 4.5g IV every 8 hours being a common first-line regimen, as recommended by the most recent guidelines 1. The choice of antibiotics should be based on local epidemiology, individual patient risk factors for difficult-to-treat pathogens, clinical severity of infection, and infection source. Some key points to consider when selecting antibiotics for abdominal infections include:

• Coverage for enteric gram-negative aerobic and facultative bacilli and enteric gram-positive streptococci 2
• Coverage for obligate anaerobic bacilli should be provided for distal small bowel, appendiceal, and colon-derived infection and for more proximal gastrointestinal perforations in the presence of obstruction or paralytic ileus 2
• Single-agent empiric therapy options include cefoxitin, ertapenem, moxifloxacin, tigecycline, and ticarcillin-clavulanic acid 3
• Combination therapy options include a cephalosporin (cefazolin, cefuroxime, ceftriaxone, cefotaxime, ciprofloxacin, or levofloxacin) in combination with metronidazole 3
• For patients with penicillin allergies, ciprofloxacin 400mg IV every 12 hours plus metronidazole is a reasonable alternative 4
• Oral step-down therapy can be considered once the patient shows clinical improvement with resolution of fever, normalization of white blood cell count, and return of bowel function 4
• The duration of antibiotic therapy should be based on the severity of the infection and the clinical response of the patient, with a typical duration of 4-7 days for uncomplicated infections and 7-14 days for complicated cases 5

From the FDA Drug Label

Piperacillin and Tazobactam for Injection is indicated in adults and pediatric patients (2 months of age and older) for the treatment of appendicitis (complicated by rupture or abscess) and peritonitis caused by beta-lactamase producing isolates of Escherichia coli or the following members of the Bacteroides fragilis group: B. fragilis, B. ovatus, B. thetaiotaomicron, or B. vulgatus.

The antibiotic used to treat abdominal infections (peritonitis) is piperacillin-tazobactam. Key points include:

• Indicated for peritonitis caused by beta-lactamase producing isolates of Escherichia coli or Bacteroides fragilis group
• Dosage: 3.375 grams every six hours, administered by intravenous infusion over 30 minutes
• Duration of treatment: 7 to 10 days 6

From the Research

Antibiotics for Abdominal Infections

The following antibiotics are used to treat abdominal infections (peritonitis):

• Broad-spectrum beta-lactam antibiotics, such as second-generation cephalosporins (e.g., cefoxitin, cefotetan) 7
• Extended-spectrum penicillin/beta-lactamase-inhibitor combinations, such as piperacillin/tazobactam 7
• Carbapenems, such as imipenem/cilastatin and meropenem, which are effective for serious infections or resistant organisms 7, 8
• Combination therapy with a third-generation cephalosporin, a monobactam (aztreonam), or an aminoglycoside plus clindamycin or metronidazole 9
• Meropenem, which has a broad spectrum of activity and is stable against chromosomal and extended-spectrum beta-lactamases 10
• Ciprofloxacin plus metronidazole, which is an effective and safe regimen for the treatment of intra-abdominal infections 11

Specific Antibiotic Regimens

Some specific antibiotic regimens that have been studied for the treatment of abdominal infections include:

• Cefoxitin, cefotetan, or cefmetazole as single-agent therapy for community-acquired infections of mild to moderate severity 9
• Carbapenems (imipenem/cilastatin) or combination therapy with a third-generation cephalosporin, a monobactam (aztreonam), or an aminoglycoside plus clindamycin or metronidazole for more severe infections 9
• Meropenem as empirical monotherapy for moderate to severe intra-abdominal infections 10
• Ciprofloxacin plus metronidazole as a combination regimen for the treatment of intra-abdominal infections 11