What antibiotics are used to treat colitis?

Antibiotic Treatment for Colitis

For Clostridium difficile colitis, oral vancomycin 125 mg four times daily for 10 days is the recommended first-line treatment, with fidaxomicin 200 mg twice daily for 10 days as an effective alternative. 1

Types of Colitis and Appropriate Antibiotic Selection

Clostridium difficile-Associated Colitis

This is the most common form of antibiotic-associated colitis requiring specific antibiotic treatment:

1. Initial episode treatment:

   • Non-severe disease:

     • First option: Oral vancomycin 125 mg four times daily for 10 days (A-I) 2, 1
     • Alternative: Oral fidaxomicin 200 mg twice daily for 10 days 1
     • If above unavailable: Oral metronidazole 500 mg three times daily for 10 days (A-I) 2, 1

   • Severe disease: (defined by fever >38.5°C, leukocytosis >15×10⁹/L, creatinine rise >50% above baseline, or pseudomembranous colitis on endoscopy)

     • Oral vancomycin 125 mg four times daily for 10 days (A-I) 2

2. When oral therapy is impossible:

   • Non-severe: Intravenous metronidazole 500 mg three times daily for 10 days (A-III) 2
   • Severe: Intravenous metronidazole 500 mg three times daily PLUS intracolonic vancomycin 500 mg in 100 mL normal saline every 4-12 hours and/or vancomycin 500 mg four times daily via nasogastric tube (A-III, C-III) 2

3. For recurrent C. difficile infection:

   • First recurrence: Same as initial episode 2
   • Second or later recurrences: Oral vancomycin 125 mg four times daily for at least 10 days, consider tapered/pulsed regimen (B-II) 2

Important Management Principles

• Always discontinue the inciting antibiotic if possible 2, 1
• Avoid antiperistaltic agents and opiates as they may worsen disease (B-II) 2, 1
• Monitor for treatment response within 3 days (decreased stool frequency, improved consistency) 2
• Consider surgical consultation for severe cases with perforation, toxic megacolon, or severe ileus not responding to antibiotics 2

Other Forms of Colitis

Inflammatory Bowel Disease (Ulcerative Colitis or Crohn's Disease)

• Antibiotics are not primary treatment for non-infectious inflammatory colitis 3
• However, test for C. difficile in IBD flares as it may complicate the disease 1
• For Crohn's disease with colonic involvement:
  • Antibiotics may have modest benefit in decreasing disease activity 3
  • Ciprofloxacin and metronidazole may be used, especially for perianal disease 3
  • Rifaximin has shown promising results 3

Antibiotic-Associated Diarrhea Without C. difficile

• Often resolves with discontinuation of the offending antibiotic 4
• Supportive care is typically sufficient 4

Common Pitfalls to Avoid

1. Using metronidazole as first-line for severe C. difficile colitis - Vancomycin has superior efficacy 1
2. Failing to test for C. difficile in patients with diarrhea after antibiotic use or hospitalization
3. Not recognizing severe disease requiring more aggressive therapy
4. Continuing the inciting antibiotic when it could be safely discontinued
5. Delaying surgical consultation in fulminant cases 2, 1

Special Considerations

• Elderly patients (>65 years) have increased risk of nephrotoxicity with oral vancomycin; monitor renal function 5
• Patients with inflammatory bowel disease require testing for C. difficile during flares 1
• Immunocompromised patients may have atypical presentations and require prompt treatment
• Recurrent C. difficile may benefit from tapered/pulsed vancomycin regimens or fecal microbiota transplantation 2

Remember that the diagnosis of the specific type of colitis is crucial for selecting the appropriate antibiotic therapy, as treatment differs significantly between infectious and non-infectious causes.