What antibiotic is recommended for spontaneous bacterial peritonitis (SBP) prophylaxis?

Norfloxacin is the First-Line Antibiotic for SBP Prophylaxis

Norfloxacin 400 mg daily is the recommended first-line antibiotic for spontaneous bacterial peritonitis (SBP) prophylaxis in cirrhotic patients with ascites, based on extensive evidence demonstrating its efficacy in reducing SBP recurrence and improving survival. 1, 2

Indications for SBP Prophylaxis

SBP prophylaxis should be initiated in the following patient populations:

1. Secondary prophylaxis (patients with prior SBP):

   • All patients who survive an episode of SBP should receive indefinite antibiotic prophylaxis until liver transplantation or resolution of ascites
   • Without prophylaxis, recurrence rate is approximately 70% at 1 year 1, 2
   • Norfloxacin reduces SBP recurrence from 68% to 20% 1

2. Primary prophylaxis (patients without prior SBP):

   • Patients with low ascitic fluid protein (<1.5 g/dL) AND advanced liver disease (Child-Pugh score ≥9 with serum bilirubin >3 mg/dL, impaired renal function, or serum sodium <130 mEq/L) 1, 2
   • Patients with cirrhosis and acute gastrointestinal bleeding (short-term prophylaxis) 2

Antibiotic Options for SBP Prophylaxis

First-Line Option:

• Norfloxacin 400 mg once daily 1, 2
  • Most extensively studied and recommended by European Association for the Study of the Liver
  • Significantly reduces SBP recurrence and improves short-term survival

Alternative Options:

1. Ciprofloxacin 500 mg once daily 2, 3, 4

   • Similar efficacy to norfloxacin
   • Weekly ciprofloxacin has been shown to be non-inferior to daily norfloxacin in some studies 3

2. Trimethoprim-sulfamethoxazole 800/160 mg daily 2, 4, 5

   • Similar efficacy to norfloxacin
   • Higher risk of adverse events (rash, hyperkalemia, bone marrow suppression)
   • Consider in patients with quinolone allergy or resistance

3. Rifaximin 550 mg twice daily 2, 6

   • Emerging evidence suggests superior efficacy for secondary prophylaxis
   • Recent randomized controlled trial showed significantly lower SBP recurrence with rifaximin compared to norfloxacin (7% vs 39%, p=0.004) 6
   • Additional benefit of reducing hepatic encephalopathy episodes

4. For patients with gastrointestinal bleeding:

   • IV ceftriaxone for 7 days (preferred in advanced liver disease)
   • Norfloxacin 400 mg twice daily for 7 days 2

Management Considerations

Duration of Prophylaxis:

• Secondary prophylaxis: Continue indefinitely until liver transplantation or resolution of ascites
• Primary prophylaxis: Continue until risk factors resolve or transplantation

Monitoring:

• Regular assessment of renal function every 1-3 months
• Periodic cultures to detect resistant organisms
• Monitor for adverse effects of antibiotics

Potential Complications:

• Long-term quinolone use has led to increasing gram-positive and multi-drug resistant infections 1, 2
• Consider alternative antibiotics if infection develops with resistant bacteria
• Fluoroquinolones can cause rare but serious musculoskeletal and nervous system side effects

Special Considerations

1. Quinolone resistance:

   • If infection develops with quinolone-resistant bacteria, consider switching to trimethoprim-sulfamethoxazole or rifaximin 2
   • Rifaximin may be particularly valuable in areas with high quinolone resistance 6

2. Hepatic encephalopathy:

   • Consider rifaximin for patients with both SBP risk and hepatic encephalopathy 6

3. Renal dysfunction:

   • For patients with active SBP, adding albumin to antibiotic therapy decreases hepatorenal syndrome risk and improves survival 7

Despite clear guidelines, SBP prophylaxis remains underutilized, with only one-third of eligible patients receiving appropriate prophylaxis after discharge 2. The evidence strongly supports prophylaxis for high-risk patients, with benefits in mortality reduction outweighing the risks of long-term antibiotic use.