Treatment for C. difficile Diarrhea

Initial Episode: Non-Severe Disease

The Infectious Diseases Society of America (IDSA) recommends oral vancomycin 125 mg four times daily for 10 days as the first-line treatment for mild-to-moderate CDI, having demonstrated superiority over metronidazole in clinical outcomes 1, 2, 3
Fidaxomicin 200 mg orally twice daily for 10 days is a conditional alternative recommendation from the 2021 IDSA/SHEA guidelines, particularly valuable for elderly patients or those with multiple comorbidities who face higher recurrence risk 1, 2
The IDSA/SHEA guidelines represent a significant shift from 2015 guidance, which previously favored metronidazole for cost reasons—this change reflects moderate-quality evidence showing vancomycin's superior efficacy 1, 4

Oral vancomycin 125 mg four times daily for 10 days remains the cornerstone, though higher doses (up to 500 mg four times daily) are sometimes used in fulminant cases based on expert opinion rather than randomized trials 4
Add intravenous metronidazole 500 mg every 8 hours as adjunctive therapy in fulminant disease or when ileus is present, since IV vancomycin does not reach the colon 4, 5
Obtain prompt surgical consultation for patients with white blood cell count ≥25,000, lactate ≥5 mmol/L, ileus, toxic megacolon, or peritoneal signs—early intervention reduces mortality 4, 3

The IDSA recommends oral vancomycin 125 mg four times daily for 10-14 days if metronidazole was used initially, or use a tapered and pulsed vancomycin regimen if standard vancomycin was used for the initial episode 6, 3
Fidaxomicin 200 mg twice daily for 10 days demonstrates lower recurrence rates (15.4%) compared to vancomycin (25.3%) and is a preferred option for first recurrence 4, 6

Fecal microbiota transplantation (FMT) is strongly recommended after failure of appropriate antibiotic treatments for at least two recurrences, with clinical resolution rates of 87-92% compared to 40-50% with antibiotics alone 6, 3
Administer oral vancomycin 125 mg four times daily for 4-10 days as lead-in therapy before FMT to reduce bacterial load 3

Discontinue the inciting antibiotic immediately if clinically possible—this is the single most important intervention beyond specific CDI treatment 3, 7
If continued antibiotics are necessary for another infection, switch to lower-risk agents: parenteral aminoglycosides, sulfonamides, macrolides, or tetracyclines/tigecycline 3, 7
Avoid high-risk antibiotics: clindamycin, third-generation cephalosporins, penicillins, and fluoroquinolones are strongly associated with CDI development and recurrence 3, 7

Watch for warning signs requiring escalation: WBC ≥25,000 or rising, lactate ≥5 mmol/L, ileus, toxic megacolon, or peritoneal signs mandate immediate surgical consultation 3

Do not use IV vancomycin for CDI treatment—it is not excreted into the colon and has no efficacy against CDI; oral vancomycin must be used 5
Do not use metronidazole as monotherapy for severe disease or any recurrent episode—it has inferior outcomes and neurotoxicity concerns 3
Do not delay surgical consultation in fulminant disease—mortality increases significantly with delayed intervention 4