COVID-19 (Coronavirus)

RifaxMax Study

Condition: Irritable bowel syndrome, diarrhea


Key Inclusion Criteria:

  • 18-75 years old
  • Meets Rome IV criteria (diagnostic criteria) for IBS-D and meets other specific criteria to progress to treatment phase
  • Colonoscopy must have been completed within the past 10 years

Key Exclusion Criteria

  • Use of any oral antibiotics in the last two months
  • History of intestinal surgery (except appendectomy or cholecystectomy)
  • Active asthma or any history of anaphylaxis

Full Study Name

Evaluation of the Efficacy and Safety of Rifaximin in Combination With N-acetylcysteine (NAC) in Adult Patients With Irritable Bowel Syndrome with Diarrhea (IRB no. 00000550)

The purpose of this study is to evaluate the investigational use of a combination of a drug called rifaximin and a dietary supplement, N-acetyl-L-cysteine (NAC), in patients with irritable bowel syndrome with diarrhea (IBS-D). Rifaximin is one of the standard treatments for IBS-D. While rifaximin is safe and effective for treating IBS-D symptoms, many patients find that their symptoms return after a period of time. The study aims to determine whether using a combination of rifaximin and NAC will more effectively decrease IBS-D symptoms than using rifaximin alone. 

NAC is used to break up mucus in the lungs; researchers hope to learn whether it can also break up the mucus layer in the small intestine and therefore potentially increase the effectiveness of rifaximin. Participants will be randomly assigned to one of three study groups. Group 1 will receive rifaximin. Group 2 will receive a lower dose of rifaximin and a placebo (inactive substance). Group 3 will receive the lower dose 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, but the two medications are approved for use separately.

Principal Investigator

Nipaporn Pichetshote, MD


Medically Associated Science and Technology (MAST) Program Office