What is the antimicrobial regimen for intra-abdominal infection?

From the Guidelines

The recommended antimicrobial regimen for intra-abdominal infections typically involves empiric broad-spectrum coverage targeting both aerobic and anaerobic organisms, with piperacillin-tazobactam 3.375g IV every 6 hours or meropenem 1g IV every 8 hours being suitable options. For community-acquired mild to moderate infections, a reasonable regimen includes ceftriaxone 1-2g IV daily plus metronidazole 500mg IV every 8 hours, or a single agent like piperacillin-tazobactam 3.375g IV every 6 hours 1.

Key Considerations

• The choice of antimicrobial regimen should be based on the severity of the infection, with broader coverage warranted for healthcare-associated or severe community-acquired infections 1.
• Treatment duration should typically be 4-7 days, provided source control (drainage or surgical intervention) has been achieved 1.
• Therapy can be discontinued when the patient has no signs of systemic inflammation, is afebrile, and has normal white blood cell count.
• For patients with risk factors for resistant organisms (recent hospitalization, prior antibiotic exposure), consider adding vancomycin 15-20mg/kg IV every 8-12 hours or an antifungal if indicated 1.

Antimicrobial Options

• Piperacillin-tazobactam 3.375g IV every 6 hours
• Meropenem 1g IV every 8 hours
• Imipenem-cilastatin 500mg IV every 6 hours
• Ceftriaxone 1-2g IV daily plus metronidazole 500mg IV every 8 hours

Important Notes

• Antimicrobial therapy should be narrowed based on culture results when available 1.
• The use of aminoglycosides or other second agents effective against gram-negative facultative and aerobic bacilli is not recommended in the absence of evidence that the patient is likely to harbor resistant organisms that require such therapy 1.

From the FDA Drug Label

14.2 Complicated Intra-abdominal Infections Tigecycline was evaluated in adults for the treatment of complicated intra-abdominal infections (cIAI) in two randomized, double-blind, active-controlled, multinational, multicenter studies (Studies 301 and 306) These studies compared tigecycline (100 mg intravenous initial dose followed by 50 mg every 12 hours) with imipenem/cilastatin (500 mg intravenous every 6 hours) for 5 to 14 days.

1.1 Intra-abdominal Infections 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 antimicrobial regimen for intra-abdominal infection includes:

• Tigecycline: 100 mg intravenous initial dose followed by 50 mg every 12 hours for 5 to 14 days 2
• Imipenem/Cilastatin: 500 mg intravenous every 6 hours for 5 to 14 days 2
• Piperacillin and Tazobactam: 3.375 g every six hours [totaling 13.5 g (12 g piperacillin/1.5 g tazobactam)] for 7 to 10 days 3

From the Research

Antimicrobial Regimen for Intra-Abdominal Infection

The antimicrobial regimen for intra-abdominal infection typically involves broad-spectrum antibiotics that cover a range of gram-negative, gram-positive, and anaerobic bacteria.

• Meropenem, a carbapenem antibacterial agent, has been shown to be effective in the treatment of intra-abdominal infections, with clinical response rates ranging from 91 to 100% in moderate to severe cases 4, 5.
• Other effective antimicrobial regimens include imipenem/cilastatin, cefotaxime plus metronidazole, and clindamycin plus tobramycin or gentamicin 4, 6, 5.
• The choice of antimicrobial regimen depends on the severity of the infection, the presence of resistant pathogens, and the patient's underlying medical conditions 7, 8.
• In patients with nosocomially-acquired intra-abdominal infections, broader spectrum antimicrobial regimens are recommended to cover more resistant gram-negative bacilli and anaerobes, as well as enterococci, resistant staphylococci, and Candida 7, 8.
• De-escalation of an initially broad antimicrobial regimen should be undertaken once definitive culture results are available to minimize the risk of antibiotic resistance and side effects 8.

Key Antimicrobial Agents

• Meropenem: a broad-spectrum carbapenem antibacterial agent with activity against gram-negative, gram-positive, and anaerobic bacteria 4, 6, 5.
• Imipenem/cilastatin: a broad-spectrum carbapenem antibacterial agent with activity against gram-negative, gram-positive, and anaerobic bacteria 4, 6.
• Cefotaxime plus metronidazole: a combination regimen with activity against gram-negative and anaerobic bacteria 4, 5.
• Clindamycin plus tobramycin or gentamicin: a combination regimen with activity against gram-positive and anaerobic bacteria, as well as gram-negative bacteria 5.