Empiric antibiotics for intra-abdominal infections

Mahitab Hany, BS Pharm, PGDipClinPharm, PGDipClinNutrition

Complicated intra-abdominal infections are problems in clinical practice and consume substantial hospital resources. New guidelines will clarify appropriate antibiotics for empiric treatment of complicated intra-abdominal infections...

Community-acquired infections

For appendicitis and other mild to moderate community infections use a single agent such as cefoxitin (Primafoxin, Plucefox) or ticarcillin/clavulanate (Timentin), OR combo therapy such as metronidazole plus cefazolin or ceftriaxone (Rocephin). Reserve tigecycline (Tygacil) because of its broader spectrum and ertapenem (Invanz) to reduce the risk of carbapenem resistance. Avoid ampicillin/sulbactam (Unasyn) due to E. coli resistance, and cefotetan and clindamycin due to increasing B. fragilis resistance, (see table 1).

Table (1). Empiric antibiotic regimens for community-acquired intra-abdominal infections in adults
Low-risk community-acquired intra-abdominal infections
ANTIBIOTIC DOSE
Single-agent regimen
Piperacillin-tazobactam 4.5 g IV every 6 hours
Combination regimen with metronidazole
One of the following...
Cefazolin 1 to 2 g IV every 8 hours
or
Cefuroxime 1.5 g IV every 8 hours
or
Ceftriaxone 2 g IV once daily
or
Cefotaxime 2 g IV every 8 hours
or
Ciprofloxacin 400 mg IV every 12 hours or500 mg PO every 12 hours
or
Levofloxacin 750 mg IV or PO once daily
Plus
Metronidazole 500 mg IV or PO every 8 hours
NOTE:
  • When piperacillin-tazobactam or one of the combination regimens in the table cannot be used, ertapenem (1 g IV once daily) is a reasonable alternative.
  • For most uncomplicated biliary infections of mild to moderate severity, the addition of metronidazole is not necessary.
High-risk community-acquired intra-abdominal infections in adults
ANTIBIOTIC DOSE
Single-agent regimen
Imipenem-cilastatin 500 mg IV every 6 hours
Meropenem 1 g IV every 8 hours
Doripenem 500 mg IV every 8 hours
Piperacillin-tazobactam 4.5 g IV every 6 hours
Combination regimen with metronidazole
ONE of the following...
Cefepime 2 g IV every 8 hours
OR
Ceftazidime 2 g IV every 8 hours
PLUS
Metronidazole 500 mg IV or PO every 8 hours

Health care-associated infections

Rely on local susceptibility patterns and use multi-drug regimens if needed. For expanded coverage of gram-negative and facultative bacilli, use agents such as meropenem (Meronem), imipenem/cilastatin (Tienam), doripenem (Doribax), or metronidazole plus cefepime, (see table 2).

  • Enterococcal infections
    • Treat empirically for enterococci if patients have a SEVERE community-acquired infection or a health care-associated infection especially after surgery. Also cover enterococci empirically in elderly, immunocompromised, or other high-risk adults.
    • Use ampicillin, piperacillin/tazobactam (Zosyn), or vancomycin to cover E. faecalis.
    • Don't empirically treat for vancomycin-resistant enterococcus (VRE) except for patients at very high risk.

Finally, limit antibiotics to 4 to 7 days if the infection source is eliminated. Longer durations don't improve outcomes. When possible, switch to oral drugs such as moxifloxacin (Avelox), amoxicillin/clavulanate (Augmentin, etc) or metronidazole PLUS ciprofloxacin (Ciprobay), levofloxacin (Tavanic), or an oral cephalosporin.

Table (2). Empiric antibiotic regimens for health care-associated intra-abdominal infections in adults
ANTIBIOTIC DOSE
Single-agent regimen
Imipenem-cilastatin 500 mg IV every 6 hours
Meropenem 1 g IV every 8 hours
Doripenem 500 mg IV every 8 hours
Piperacillin-tazobactam 4.5 g IV every 6 hours
Combination regimen
ONE of the following...
Cefepime 2 g IV every 8 hours
OR
Ceftazidime 2 g IV every 8 hours
PLUS
Metronidazole 500 mg IV or PO every 8 hours
PLUS ONE of the following (in some cases, SEE NOTE BELOW)...
Ampicillin 2 g IV every 4 hours
OR
Vancomycin 15 to 20 mg/kg IV every 8 to 12 hours
NOTE:
  • We add ampicillin or vancomycin to a cephalosporin-based regimen to provide enterococcal coverage, particularly in those with postoperative infection, prior use of antibiotics that select for Enterococcus, immunocompromising condition, valvular heart disease, or prosthetic intravascular materials.
  • Coverage against vancomycin-resistant enterococci (VRE) is generally not recommended, although it is reasonable in patients who have a history of VRE colonization or in liver transplant recipients who have an infection of hepatobiliary source.

References

  • Gelot S, Nakhla E (2016). Intra-abdominal Infections in Adults. US Pharm. 2016;41(4):HS5-HS12. Available at: https://www.uspharmacist.com/article/intraabdominal-infections-in-adults

    Solomkin JS, Mazuski JE, Bradley JS, Rodvold KA, Goldstein EJ, Baron EJ, O'Neill PJ, Chow AW, Dellinger EP, Eachempati SR, Gorbach S, Hilfiker M, May AK, Nathens AB, Sawyer RG, Bartlett JG. Diagnosis and management of complicated intra-abdominal infection in adults and children: guidelines by the Surgical Infection Society and the Infectious Diseases Society of America. Clin Infect Dis. 2010 Jan 15;50(2):133-64. Available at: https://academic.oup.com/cid/article/50/2/133/327316?login=false

    Montravers P, Lepape A, Dubreuil L, Gauzit R, Pean Y, Benchimol D, Dupont H. Clinical and microbiological profiles of community-acquired and nosocomial intra-abdominal infections: results of the French prospective, observational EBIIA study. J Antimicrob Chemother. 2009 Apr;63(4):785-94. Available at: https://academic.oup.com/jac/article/63/4/785/710992?login=false

    Solomkin JS, Mazuski JE, Baron EJ, Sawyer RG, Nathens AB, DiPiro JT, Buchman T, Dellinger EP, Jernigan J, Gorbach S, Chow AW, Bartlett J; Infectious Diseases Society of America. Guidelines for the selection of anti-infective agents for complicated intra-abdominal infections. Clin Infect Dis. 2003 Oct 15;37(8):997-1005. Available at: https://academic.oup.com/cid/article/37/8/997/436091?login=false