Best Antibiotic for Spontaneous Bacterial Peritonitis
Intravenous cefotaxime 2 g every 8 hours is the best antibiotic for treating spontaneous bacterial peritonitis in adults with cirrhosis and ascites. 1
First-Line Treatment: Third-Generation Cephalosporins
Cefotaxime remains the gold standard for empiric treatment of community-acquired SBP, with Class I, Level A evidence supporting its use. 1 The recommended regimen is:
- Cefotaxime 2 g IV every 8 hours for 5-10 days (5 days is sufficient for most uncomplicated cases) 1, 2
- Resolution rates: 69-98% 2, 3
- Non-nephrotoxic with excellent ascitic fluid penetration 4, 5
Ceftriaxone is an equally effective alternative:
- 1 g IV every 12-24 hours or 2 g IV once daily 1, 2
- Resolution rates: 73-100% 2
- More convenient dosing schedule 2
The evidence strongly supports both agents as interchangeable first-line options, with cefotaxime being more extensively studied historically but ceftriaxone offering practical dosing advantages. 3, 6
Alternative Oral Therapy (Selected Patients Only)
Oral ofloxacin 400 mg twice daily can substitute for IV cefotaxime, but ONLY in patients who meet ALL of the following criteria: 1
- No prior quinolone exposure
- No vomiting
- No shock
- No grade II or higher hepatic encephalopathy
- Serum creatinine <3 mg/dL 1
This option applies to only 61% of SBP patients, so most will require IV therapy. 1
Critical Adjunctive Therapy: Albumin
Always administer IV albumin in addition to antibiotics for patients with ANY of these high-risk features: 1, 2
- Serum creatinine ≥1 mg/dL
- Blood urea nitrogen ≥30 mg/dL
- Total bilirubin ≥4 mg/dL
Albumin dosing:
This intervention reduces mortality from 29% to 10% and prevents hepatorenal syndrome. 1, 2 Albumin is superior to hydroxyethylstarch for this indication. 1
Nosocomial SBP: Different Approach Required
For hospital-acquired SBP, third-generation cephalosporins have unacceptably high failure rates due to resistant organisms. 7
Meropenem 1 g IV every 8 hours PLUS daptomycin 6 mg/kg/day is significantly more effective than ceftazidime for nosocomial SBP (86.7% vs 25% resolution rate, P<0.001). 7 This represents the single highest-quality recent study addressing nosocomial SBP and should guide practice in this setting.
Treatment Duration and Monitoring
Standard duration: 5 days for uncomplicated cases 1, 2
- A randomized trial demonstrated 5 days is as effective as 10 days 1
- Extend beyond 5 days only if inadequate clinical response or resistant organisms 2
Perform repeat paracentesis at 48 hours to assess treatment response: 1, 2
- Treatment failure = PMN count decrease <25% from baseline 7
- If treatment fails, suspect resistant organisms or secondary peritonitis 2
Common Pitfalls and Caveats
Do NOT use quinolones (ciprofloxacin, ofloxacin) as first-line therapy if: 1, 2
- Patient has received quinolone prophylaxis (high resistance rates)
- Patient has severe presentation (shock, renal failure, encephalopathy)
- Nosocomial acquisition (resistance common)
Distinguish SBP from secondary peritonitis by checking ascitic fluid: 1
- Total protein >1 g/dL
- LDH > upper limit of normal for serum
- Glucose <50 mg/dL
- Multiple organisms on culture
If ≥2 of these criteria are present, suspect gut perforation and add anaerobic coverage plus surgical consultation. 1
Ceftriaxone has high protein binding, which theoretically limits penetration into low-protein ascitic fluid, but this has not proven clinically significant in practice. 1, 2
Post-Treatment Prophylaxis
All patients who survive SBP require indefinite prophylaxis until liver transplantation or death: 2