Efficacy of Rifaximin With NAC in IBS-D

Part of paid clinical trials in Los Angeles, California.

Sponsor
Mark Pimentel, MD
Study ID
NCT06727422
Phase
PHASE2
Status
Recruiting
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Conditions

  • IBS (Irritable Bowel Syndrome)
  • IBS-D (Diarrhea-predominant)

Eligibility Criteria

Sex
ALL
Age
18 Years - N/A
Healthy Volunteers
Not accepted

Interventions

  • rifaximin 66mg + N-acetylcysteine 560mg three times daily — DRUG
    RNIB21 containing rifaximin 66mg + N-acetylcysteine 560mg three times daily
  • RNIB21 containing rifaximin 132mg + N-acetylcysteine 560mg three times daily — DRUG
    RNIB21 containing rifaximin 132mg + N-acetylcysteine 560mg three times daily
  • Placebo — DRUG
    placebo three times daily

Study Details

The purpose of this study is to examine the effectiveness of using a combination of a drug, rifaximin and a dietary supplement, N-acetyl-L-cysteine (NAC), to treat patients with irritable bowel syndrome with diarrhea (IBS-D). Rifaximin is one of the standard treatments for IBS-D and is FDA approved. While rifaximin is safe and effective for treating symptoms in patients with IBS-D, many patients find that their symptoms may not completely resolve, or may come back after a period of time. This research study is designed to test the investigational use of a combination of rifaximin and NAC. The combination of rifaximin and NAC is not approved by the U.S. Food and Drug Administration (FDA) for the treatment of IBS-D, and the effects of taking both medications together are unknown. However, the two medications are approved for use separately, as detailed below. Rifaximin is the only antibiotic approved by the FDA for the treatment of IBS-D. Rifaximin (at a dose of 550 mg by mouth three times daily for 14 days) is approved by the FDA for the treatment of IBS-D. Rifaximin (at a dose of 200 mg per mouth three times daily for 3 days) is FDA approved for the treatment of traveler's diarrhea. Rifaximin at a dose of 200 mg per mouth three times daily is not approved by the FDA for the treatment of IBS-D. NAC is approved by the FDA to treat acetaminophen overdose (72-hour oral and 21-hour intravenous (IV) regimens), and for use in breaking up mucus in the lungs in patients with chronic obstructive pulmonary disease (COPD) and other lung conditions such as bronchitis. NAC is also available over-the-counter in 600 mg and 900 mg capsules as a dietary supplement, although over-the-counter use is not regulated by the FDA. This study will utilize the 600 mg dietary supplement capsules. The Investigators want to know if using a combination of rifaximin and NAC will give better results in decreasing IBS-D symptoms than using rifaximin alone. As NAC is used to break up mucus in the lungs, and the Investigators want to see if this can also break up the mucus layer in the small intestine, and therefore potentially increase the effectiveness of rifaximin. The Investigators will be testing 2 doses to determine which dose is most effective. participants are being asked to take part in this research study because participants were diagnosed with IBS-D.

Key Dates

Start date
Feb 4, 2026
Status verified
Apr 2026
Primary completion
Aug 1, 2026
Completion
Jan 1, 2027

Study Design

Enrollment
225 participants (estimated)
Allocation
RANDOMIZED
Intervention model
PARALLEL
Primary purpose
TREATMENT

Arms

  • Experimental: low dose for IBS-D
    RNIB21 containing rifaximin 66mg + NAC 560mg three times a day
  • Experimental: high dose for IBS-D
    RNIB21 containing rifaximin 132mg + NAC 560mg three times a day
  • Placebo Comparator: placebo
    placebo three times a day

Primary Outcome Measure

stool consistency [ Time Frame: 2 weeks ]

Central Contacts

Locations (1)

FacilityCityStateZIPSite coordinators
Cedars-Sinai Medical CenterLos AngelesCalifornia90048
Ava Hosseini
[email protected]
3104230617

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By research site
Cedars-Sinai Medical Center· Los Angeles, CA

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