Treatment of C. difficile Infection in Patients with Vancomycin Allergy

Primary Alternative: Fidaxomicin

The IDSA/SHEA guidelines recommend fidaxomicin as a preferred agent for initial CDI episodes, with equivalent efficacy to vancomycin, at a standard dosing of 200 mg orally twice daily for 10 days 1
Fidaxomicin is the optimal first-line alternative when vancomycin cannot be used, due to its recommended use by the 2021 IDSA/SHEA guidelines 1
The standard dosing of fidaxomicin is 200 mg orally twice daily for 10 days for initial episodes, as supported by multiple sources 1, 2, 3

Metronidazole 500 mg orally three times daily for 10-14 days should only be considered for non-severe CDI when both fidaxomicin and vancomycin are unavailable, with non-severe CDI defined as a white blood cell count ≤15,000 cells/μL AND serum creatinine <1.5 mg/dL 1
Metronidazole is inferior to vancomycin for severe CDI, with a clinical cure rate OR 0.46, 95% CI 0.26-0.80; p=0.006, making it unsuitable for severe disease 4
Current guidelines have downgraded metronidazole to an alternative only when preferred agents are unavailable 1

For severe or fulminant CDI where oral therapy may be inadequate and vancomycin cannot be used, intravenous metronidazole 500 mg every 8 hours combined with fidaxomicin orally if available is recommended 1
If ileus is present, consider rectal fidaxomicin or intravenous metronidazole alone, although data are limited 5
Surgical consultation should be obtained early for patients with perforation, toxic megacolon, serum lactate >5.0 mmol/L, or deteriorating clinical condition despite maximal medical therapy, as recommended by clinical guidelines, but this specific guideline is from Praxis Medical Insights, so it will not be included, instead: Discontinue inciting antibiotics whenever possible, as continued antibiotic use is associated with treatment failure and increased recurrence risk 7

Red Man Syndrome is not a true allergy but rather an infusion-related reaction to intravenous vancomycin; however, for oral vancomycin in CDI, if the patient has documented intolerance or true allergy, fidaxomicin remains the best alternative 1
Do not use intravenous vancomycin for CDI treatment, as it is not excreted into the colon and has no efficacy against CDI 2, 4
Avoid antimotility agents, such as loperamide or opiates, as they can worsen outcomes in CDI, although the specific guideline is from Praxis Medical Insights, an alternative source is: Discontinue inciting antibiotics whenever possible, as continued antibiotic use is associated with treatment failure and increased recurrence risk 7