Prophylaxis for Spontaneous Bacterial Peritonitis (SBP)

SBP prophylaxis is divided into secondary (after a prior episode) and primary (before any episode, based on risk factors). The underlying mechanism of all antibiotic prophylaxis is selective intestinal decontamination - eliminating gram-negative enteric organisms that translocate into ascitic fluid.

1. Secondary Prophylaxis (Most Important Indication)

Who: All patients who have survived a prior SBP episode. Risk of recurrence without prophylaxis is ~70% within 1 year.

Drug	Dose	Notes
Ciprofloxacin	500 mg orally once daily	Preferred in most guidelines (norfloxacin withdrawn from US market in 2014)
Rifaximin	600 mg orally twice daily	Reasonable alternative; also used for hepatic encephalopathy prophylaxis
Trimethoprim-sulfamethoxazole	1 DS tablet daily (5 days/week)	Alternative where fluoroquinolones unavailable

Long-term (indefinite) prophylaxis is the standard - until liver transplantation or death - because the underlying liver disease is not corrected.

2. Primary Prophylaxis

Who: Two specific high-risk groups warrant long-term primary prophylaxis:

Low ascites protein + advanced liver/circulatory dysfunction: ascites total protein < 1 g/L (some guidelines use < 1.5 g/L) plus at least one of:
- Bilirubin > 3 mg/dL (jaundice)
- Serum sodium < 130 mEq/L (hyponatremia)
- Serum creatinine > 1.2 mg/dL or BUN > 25 mg/dL (renal dysfunction)
- Child-Pugh score >= 9
Acute GI variceal hemorrhage: Short-term prophylaxis (7 days) with IV ceftriaxone 1 g/day during hospitalization, then oral norfloxacin/ciprofloxacin. This is technically infection prophylaxis broadly (including SBP), and reduces mortality.

3. Drug of Choice Summary

Norfloxacin 400 mg/day was the historical gold standard but was withdrawn from the US market in 2014
Ciprofloxacin 500 mg/day (oral) is the current preferred fluoroquinolone alternative
Rifaximin 600 mg twice daily is a well-tolerated non-absorbable antibiotic alternative
Avoid aminoglycosides (nephrotoxic in cirrhosis)

4. Albumin as Adjunct (During Active SBP Treatment)

While not prophylaxis per se, albumin IV reduces hepatorenal syndrome risk during active SBP:

1.5 g/kg at diagnosis + 1 g/kg on day 3
Indicated when BUN > 30, creatinine > 1 mg/dL, or bilirubin > 4 mg/dL
Do not exceed 100 g per dose

5. Important Caveats

Widespread antibiotic prophylaxis has led to increased multidrug-resistant organisms causing SBP. In healthcare-associated or nosocomial SBP, broader-spectrum antibiotics (vancomycin-piperacillin-tazobactam, imipenem, ertapenem) should be used empirically.
Prophylaxis is indefinite once started in secondary prevention - it does not cure the underlying portal hypertension and bacterial translocation.
Liver transplantation remains the only definitive management.

Sources:

Goldman-Cecil Medicine, 26th ed. (Chapter 139 - Cirrhosis and Its Sequelae), blocks 18-19
Norfloxacin vs. alternatives meta-analysis: Song et al., BMC Infect Dis 2023 (PMID 37641014) - confirmed non-inferiority of fluoroquinolone alternatives

This is a shared conversation. Sign in to Orris to start your own chat.