Table 1.

Classification and pharmacologic management of CDI.

Classification	Criteria	Treatment options
Primary CDI, non-severe	Diarrhea without signs of systemic infection, WBC <15,000 cells/mL, and serum creatinine <1.5 times the premorbid level	metronidazole 500 mg by mouth three times daily for 10–14 days OR vancomycin 125 mg by mouth three times daily for 10–14 days OR fidaxomicin 200 mg by mouth twice daily for 10 daysa
Primary CDI, severe	Signs of systemic infection and/or WBC ≥15,000 cells/mL, or serum creatinine ≥1.5 times the premorbid level	vancomycin 125 mg by mouth three times daily for 10–14 days OR fidaxomicin 200 mg by mouth twice daily for 10 daysa
Primary CDI, complicated	signs of systemic infection including hypotension, ileus, or megacolon	vancomycin 500 mg by mouth four times daily AND intravenous metronidazole 500 mg three times daily AND (if ileus is present) vancomycin 500 mg by rectum four times daily
Recurrent CDI	Return of symptoms with positive C. difficile testing within 8 weeks of onset, but after initial symptoms resolved with treatment	First recurrence: same as initial treatment, based on severity. Second recurrence: Start treatment based on severity, followed by a vancomycin pulsed and/or tapered regimen over six or more weeks

Footnotes.

^afidaxomicin is not currently represented in US guidelines (49) but is FDA-approved for the treatment of CDI.

Abbreviations: CDI, Clostridium difficile infection; WBC, white blood cell count.