What antibiotics are used to treat colitis, including infectious colitis and inflammatory bowel disease (IBD)?

Antibiotic Treatment for Colitis

For C. difficile colitis, use oral vancomycin 125 mg four times daily for 10 days in severe disease, and oral metronidazole 500 mg three times daily for 10 days in non-severe disease; antibiotics are NOT recommended for inflammatory bowel disease-related colitis unless C. difficile is confirmed. 1, 2

Treatment Algorithm by Colitis Type

C. difficile Colitis

Assess disease severity first to determine appropriate antibiotic choice 1, 2:

Severe C. difficile colitis (fever, rigors, hemodynamic instability, WBC >15 × 10^9/L, elevated creatinine or lactate, pseudomembranous colitis on endoscopy):

• Oral vancomycin 125 mg four times daily for 10 days 1, 2, 3
• Alternative: Teicoplanin 100 mg twice daily if vancomycin unavailable 1

Non-severe C. difficile colitis (stool frequency <4 times daily, WBC <15 × 10^9/L, no signs of severe colitis):

• Oral metronidazole 500 mg three times daily for 10 days 1, 2
• However, in patients with ulcerative colitis and non-severe C. difficile, vancomycin is superior to metronidazole, resulting in fewer readmissions (0% vs 31%) and shorter hospital stays 4

Recurrent C. difficile colitis (second episode or later):

• Oral vancomycin 125 mg four times daily for at least 10 days, with consideration of taper/pulse strategy 1, 2
• Alternative: Fidaxomicin 200 mg twice daily for 10 days 1

Severe C. difficile when oral therapy impossible:

• IV metronidazole 500 mg three times daily PLUS intracolonic vancomycin 500 mg in 100 mL normal saline every 4-12 hours 1, 2
• Can also add vancomycin 500 mg four times daily by nasogastric tube 1

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

No antibiotic regimen is recommended for ulcerative colitis, including acute severe disease 1, 2:

• A randomized controlled trial in 39 patients with acute severe ulcerative colitis showed no benefit from metronidazole and tobramycin 1
• Antibiotics have limited efficacy in luminal IBD 5

Critical Management Principles

Always test for C. difficile in IBD patients with colitis flares before concluding antibiotics are unnecessary, as IBD patients have increased risk of C. difficile co-infection 1:

• If using metronidazole empirically while awaiting C. difficile results, discontinue immediately if testing is negative 1

Discontinue the inciting antibiotic immediately if colitis was clearly antibiotic-induced, particularly in mild cases 1, 2

Avoid antiperistaltic agents and opiates entirely as these worsen outcomes in C. difficile colitis 1, 2

Consider surgical intervention (colectomy) for 1, 2:

• Perforation of the colon
• Toxic megacolon
• Severe ileus
• Systemic inflammation with deteriorating clinical condition not responding to antibiotics
• Serum lactate exceeding 5.0 mmol/L 1

Common Pitfalls

Monitor for systemic absorption in high-risk patients: Oral vancomycin can achieve clinically significant serum concentrations in patients with inflammatory intestinal mucosa, renal insufficiency, or those receiving concomitant aminoglycosides 3

Monitor renal function in elderly patients: Nephrotoxicity risk increases in patients >65 years of age, even with normal baseline renal function; monitor during and after treatment 3

Do not use IV vancomycin for C. difficile colitis: Parenteral vancomycin is not effective for C. difficile-associated diarrhea; oral administration is required 3