Medication Summary
The goals of pharmacotherapy in patients with spontaneous bacterial peritonitis (SBP) are to reduce morbidity and prevent complications. Antibiotics are initially chosen empirically, as these patients may die from overwhelming infection if treatment is delayed until culture results become available. [4]
Probiotic therapy in conjunction with antimicrobial treatment does not improve efficacy in the treatment of spontaneous bacterial peritonitis, as was found in a double-blind, placebo-controlled, randomized-controlled trial. [27] In this study, Pande et al found over a 28-month period that 110 patients who were randomized to either norfloxacin 400 mg with probiotics or placebo did not have improved efficacy in primary or secondary prophylaxis or in reducing mortality in cirrhotic patients with ascites.
Antimicrobials
Class Summary
Traditionally, a combination of an aminoglycoside and ampicillin was used to treat spontaneous bacterial peritonitis (SBP). This regimen affords excellent empiric coverage of more than 90% of cases of spontaneous bacterial peritonitis caused by gram-negative aerobes or gram-positive cocci.
More recently, the third-generation cephalosporin cefotaxime has been demonstrated to be as efficacious as the ampicillin/aminoglycoside combination, and it does not carry the increased risk of nephrotoxicity in cirrhotic patients. Cefotaxime does not cover enterococci (up to 5% of cases).
Cefotaxime (Claforan) and ceftriaxone (Rocephin)
A third-generation cephalosporin with broad gram-negative spectrum, cefotaxime has lower efficacy against gram-positive organisms and higher efficacy against resistant organisms. Thus, it provides excellent empiric coverage of SBP. By binding to 1 or more penicillin-binding proteins, cefotaxime arrests bacterial cell wall synthesis and inhibits bacterial growth.
Multiresistant bacteria (including extended-spectrum beta-lactamases (ESBL)–producing Enterobacteriaceae) are increasingly being isolated in nosocomial (and, to a lesser extent, healthcare-acquired) infections among patients with cirrhosis, which renders third-generation cephalosporins clinically ineffective. This calls for new antimicrobial strategies with a tailored approach according to local epidemiological patterns in order to best determine empirical treatment. [21]
Risk factors for multiresistant organisms include nosocomial origin of infection, long-term norfloxacin prophylaxis, recent infection with multiresistant bacteria, and recent use of beta-lactam antibiotics. Infections with resistant organisms are associated with higher mortality. It is also prudent to limit prophylactic antibiotics to patients with well-defined criteria for spontaneous bacterial peritonitis prophylaxis, to limit duration of antibiotic treatment for infections, and to narrow the spectrum of coverage once susceptibility testing results are available. [22]
Gentamicin
Gentamicin is an aminoglycoside antibiotic effective against Pseudomonas aeruginosa; E coli; and Proteus, Klebsiella, and Staphylococcus species. Dosing regimens are numerous; adjust dose based on creatinine clearance (CrCl) and changes in volume of distribution. Gentamicin may be given IV or IM.
Ampicillin
Ampicillin interferes with bacterial cell wall synthesis during active multiplication, causing bactericidal activity against susceptible organisms.
Norfloxacin (Noroxin)
Norfloxacin is used for prophylaxis in the outpatient setting (400 mg/d). It is a fluoroquinolone with activity against pseudomonads, streptococci, MRSA, S epidermidis, and most gram-negative organisms, but it has no activity against anaerobes. It inhibits bacterial DNA synthesis and, consequently, growth.
Ciprofloxacin (Cipro)
Ciprofloxacin is used for prophylaxis in the outpatient setting (750 mg weekly). It is a fluoroquinolone that inhibits bacterial DNA synthesis and, consequently, growth, by inhibiting DNA gyrase and topoisomerases, which are required for replication, transcription, and translation of genetic material. Quinolones have broad activity against gram-positive and gram-negative aerobic organisms. This agent has no activity against anaerobes.
Sulfamethoxazole and trimethoprim (Bactrim DS, Septra DS)
This agent is used as prophylaxis in the outpatient setting (5 doses of double-strength trimethoprim-sulfamethoxazole per week (Monday through Friday). It inhibits bacterial growth by inhibiting the synthesis of dihydrofolic acid.
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Gram-negative Escherichia coli.
