for people ages 18 years and up (full criteria)
study started
estimated completion



The purpose of this study is to determine whether fidaxomicin and vancomycin followed by taper and pulse vancomycin treatment are superior to standard vancomycin treatment for the treatment of recurrent Clostridium difficile infection.

Official Title

CSP #596 - Optimal Treatment for Recurrent Clostridium Difficile Infection


Abstract Clostridium difficile is the most common cause of healthcare-associated infectious diarrhea among adults in industrialized countries. In addition to diarrhea, C. difficile infection (CDI) may also result in serious complications such as shock, toxic megacolon, colectomy, and death. The Centers for Disease Control and Prevention (CDC) has estimated C. difficile results in 250,000 hospital infections, 14,000 deaths, and $1 billion in excess costs annually. Recurrent CDI is the most challenging clinical dilemma facing clinicians who treat this disease. An estimated 30% of patients who respond to initial treatment with either vancomycin or metronidazole develop recurrent CDI, usually within 1-4 weeks of completing treatment. The primary objective of this study is to determine whether 1) standard fidaxomicin treatment and 2) standard vancomycin treatment followed by taper and pulse vancomycin treatment are superior to standard vancomycin treatment alone for sustained clinical response at day 59 for all treatments, for participants with either their first or second recurrence of CDI. Veterans presenting with a first or second CDI recurrence will be screened, consented and randomly assigned in a double-blind manner equally to one of three treatment groups: 1) a 10 day course of oral vancomycin (VAN-TX), 2) a 10 day course of fidaxomicin (FID-TX) or 3) a 31 day course of vancomycin which includes a taper and pulse following daily treatment (VAN-TP/P). Symptom resolution is defined as an improvement or resolution of diarrhea ( 3 unformed bowel movements over 24 hours) for 48 consecutive hours compared to the participant's baseline. Recurrence is defined as having diarrhea (>3 loose or semi-formed stools over 24 hours for 48 consecutive hours). A sample size of 549 randomized study participants is required to obtain 91% global power to detect a 16% absolute difference (expected proportion of 31% in the VAN-TX group) in sustained clinical response (D- COM) proportion for at least one comparison (VAN-TP/P vs. VAN-TX, FID-TX vs. VAN-TX) at the family wised error rate (FWER) 0.05 level. The marginal probability (disjunctive power) of detecting 16% absolute difference for each comparison is 81%. The expected withdrawal rate prior to day 59 (prior outcome assessment) is estimated to be 10%. If both FID-TX and VAN-TP/P are found to be superior to VAN-TX, then the non-inferiority of VAN-TP/P to FID-TX will be assessed. With the assumption that sites recruit 6 participants (site average) per year for sites primarily recruiting from the main hospital and nearby CBOCS, and 9 participants (site average) per year for sites that could partner with independent VAMCs (Independent VAMCs LSI Application will be reviewed and approved by Central IRB) that are close in distance to allow a shared site coordinator (WOC appointed) at an increased funding level, the study is expected to complete enrollment of 549 participants within 6 years with 90 days of follow-up. This includes 2 years of pilot phase plus transitioning period from pilot phase to full study, and 4 years of full study. There were 6 sites in the pilot phase and will have 24 units (26 sites) in full phase (including 5 pilot sites and 21 additional sites). Sites that are significantly below the recruitment target for an extensive period may be considered for termination. The recruitment timeline and the number of sites will be re-evaluated based on the actual recruitment rate, the number of sites still recruiting, whether replacement or additional sites will be added, the study time period on administrative recruitment hold due to COVID-19 pandemic, and available funding resources.


Clostridium Difficile Fidaxomicin Vancomycin Recurrent Pulse Taper Vancomycin with Taper/Pulse Vancomycin T/P


You can join if…

Open to people ages 18 years and up

  • Informed consent obtained and signed
  • Age > 18
  • If female, participant must not be pregnant or nursing
  • Negative pregnancy test required for females <61 years of age or without prior hysterectomy
  • Confirmed current diagnosis of CDI, determined by having
  • >3 loose or semi-formed stools for participants over 24 hours AND
  • Positive stool assay for C. difficile
  • EIA positive for toxin A/B; or
  • Cytotoxin assay; or
  • Nucleic Acid Amplification Test (NAAT, PCR or LAMP) based detection of toxigenic
  • difficile
  • Current episode represents the first recurrent episode of CDI within 3 months of the primary CDI episode in a patient who has not had CDI in the 3 months prior to the primary episode OR a second recurrent CDI episode occurring within 3 months of the first recurrent episode, as defined above
  • At least one of the previous CDI episodes must have been confirmed by a stool assay for C. difficile

You CAN'T join if...

  • Inability to provide informed consent
  • Inability to take oral capsules
  • Receipt of >72 hours of antibiotics considered effective in the treatment of CDI, including:
  • metronidazole
  • vancomycin
  • fidaxomicin
  • nitazoxanide
  • rifaximin
  • Prior infusion of bezlotoxumab within the previous 6 months
  • Known presence of fulminant CDI, including hypotension, severe ileus or GI obstruction or incipient toxic megacolon
  • Receipt of more than a single course of oral vancomycin, fidaxomicin, or a vancomycin tapering regimen since the primary episode of CDI as defined above
  • Known allergy to vancomycin or fidaxomicin
  • Acute or chronic diarrhea due to inflammatory bowel disease or other cause (e.g., presence of an ileostomy or colostomy) that would confound evaluation of response to CDI treatment
  • Anticipation of need for long term systemic antibiotic treatment (beyond 7 days)
  • Patients with an active diagnosis of COVID-19 will be excluded from the study, but patients who have recovered (per current CDC guidance on discontinuation of transmission-based precautions) can be included in the study.


  • VA San Diego Healthcare System, San Diego, CA accepting new patients
    San Diego California 92161 United States
  • VA Long Beach Healthcare System, Long Beach, CA accepting new patients
    Long Beach California 90822 United States
  • VA Greater Los Angeles Healthcare System, West Los Angeles, CA terminated
    West Los Angeles California 90073 United States


accepting new patients
Start Date
Completion Date
VA Office of Research and Development
Phase 4
Study Type
Last Updated