What antibiotics are used to treat colitis?

Antibiotic Treatment for Colitis

The first-line antibiotics for colitis depend on the specific type, with metronidazole 500 mg three times daily orally for 10 days recommended for non-severe Clostridium difficile colitis, and vancomycin 125 mg four times daily orally for 10 days recommended for severe C. difficile colitis. 1

Types of Colitis Requiring Antibiotics

Clostridium difficile-Associated Colitis

• C. difficile is the primary cause of pseudomembranous colitis, most commonly associated with prior antibiotic use 2
• Classification of severity guides antibiotic selection:
  • Non-severe: stool frequency <4 times daily, no signs of severe colitis, WBC <15 × 10^9/L 3
  • Severe: fever, rigors, hemodynamic instability, peritonitis, ileus, marked leukocytosis (>15 × 10^9/L), elevated creatinine/lactate, pseudomembranous colitis on endoscopy 3

Treatment Algorithm for C. difficile Colitis

Initial Episode and First Recurrence

• Non-severe C. difficile colitis:

  • Oral therapy: Metronidazole 500 mg three times daily for 10 days (A-I) 3, 1
  • If oral therapy impossible: Metronidazole 500 mg three times daily intravenously for 10 days (A-III) 3

• Severe C. difficile colitis:

  • Oral therapy: Vancomycin 125 mg four times daily for 10 days (A-I) 3, 1, 4
  • If oral therapy impossible: Metronidazole 500 mg three times daily intravenously for 10 days (A-III) PLUS intracolonic vancomycin 500 mg in 100 mL normal saline every 4-12 hours (C-III) and/or vancomycin 500 mg four times daily via nasogastric tube (C-III) 3

Second Recurrence and Beyond

• Oral therapy: Vancomycin 125 mg four times daily for at least 10 days (B-II) 3, 1
• Consider taper/pulse strategy (e.g., decreasing daily dose with 125 mg every 3 days or a dose of 125 mg every 3 days for 3 weeks) (B-II) 3
• If oral therapy impossible: Metronidazole 500 mg three times daily intravenously for 10-14 days (A-III) plus intracolonic vancomycin 500 mg in 100 mL normal saline every 4-12 hours (C-III) 3
• Teicoplanin 100 mg twice daily can replace oral vancomycin if available 3, 1

Inflammatory Bowel Disease-Associated Colitis

• Antibiotics are not first-line therapy for ulcerative colitis 1, 5
• For ulcerative colitis, most trials did not show benefit with antibiotics, though meta-analyses suggest modest improvement in clinical symptoms 5
• For pouchitis (inflammation of the ileal pouch after colectomy for ulcerative colitis), antibiotics do show clinical benefit 5

Important Considerations

General Management Principles

• Discontinue the inciting antibiotic if possible 3, 1, 2
• Avoid antiperistaltic agents and opiates in C. difficile colitis (B-II) 3, 1
• Monitor for complications such as toxic megacolon, perforation, or peritonitis 2, 6
• Consider colectomy for perforation, systemic inflammation not responding to antibiotics, toxic megacolon, or severe ileus 3, 1

Special Populations

• Elderly patients (>65 years) have increased risk of nephrotoxicity with vancomycin 4
• Monitor renal function during and after treatment with vancomycin in elderly patients 4
• For pediatric patients (<18 years), the usual daily dosage for C. difficile colitis is 40 mg/kg in 3-4 divided doses for 7-10 days, not to exceed 2g daily 4

Potential Adverse Effects

• Vancomycin: nephrotoxicity, ototoxicity, severe dermatologic reactions (TEN, SJS, DRESS) 4
• Metronidazole: peripheral neuropathy, metallic taste, disulfiram-like reaction with alcohol 2
• Recurrent C. difficile infection occurs in 5-50% of treated patients 2
• Risk of developing antibiotic resistance with prolonged or recurrent courses 5

Infection Control

• Implement enteric isolation precautions for patients with C. difficile colitis to prevent nosocomial transmission 2
• C. difficile spores are highly resistant to many disinfectants and antibiotics 3, 6

Diagnostic Considerations

• Diagnosis of C. difficile colitis relies on:
  • Stool tests for C. difficile toxins 7, 2
  • Sigmoidoscopy or colonoscopy to visualize pseudomembranes 7, 2
• Distinguish from non-C. difficile antibiotic-associated diarrhea, which does not require specific antibiotic treatment 7