New Drug Reviews

Rifaximin (Xifaxan) for Irritable Bowel Syndrome


Am Fam Physician. 2017 Feb 15;95(4):258-259.

Rifaximin (Xifaxan) is an oral antibiotic previously marketed for the treatment of traveler's diarrhea and hepatic encephalopathy. It is now also labeled for the treatment of irritable bowel syndrome (IBS) with diarrhea.1 Rifaximin has activity against anaerobic, gram-positive, and gram-negative bacteria, including Clostridium difficile. It is not systemically absorbed and is active only in the gastrointestinal tract. It may work by reducing bacterial byproducts and altering intestinal microbiota.2

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DrugDosageDose formCost*

Rifaximin (Xifaxan)

500 mg orally three times per day for 14 days

500 mg tablets


*—Estimated retail price of 14 days of treatment based on information obtained at (accessed December 6, 2016).

DrugDosageDose formCost*

Rifaximin (Xifaxan)

500 mg orally three times per day for 14 days

500 mg tablets


*—Estimated retail price of 14 days of treatment based on information obtained at (accessed December 6, 2016).


Serious adverse effects from rifaximin are rare (less than 1%).3 It should not be used in patients with severe hepatic impairment and rarely causes C. difficile–associated colitis. Rifaximin does not alter the pharmacokinetics of a single dose of oral contraceptives, but its effect on daily oral contraceptive use is uncertain. Taking rifaximin with cyclosporine (Sandimmune) dramatically increases systemic availability of rifaximin (124-fold),1 although the clinical significance of this is unknown.

Rifaximin is a U.S. Food and Drug Administration pregnancy risk category C drug, and its safety for use in breastfeeding women is unknown.


Rifaximin is well tolerated, which is partially because of no systemic absorption. In controlled trials, the discontinuation rates because of adverse reactions were similar between rifaximin and placebo (0.4%).1 Rare adverse effects include diarrhea, loss of taste, anorexia, nausea, and irritation of nasal passages.1


In those who have IBS with diarrhea that consists of ab

Address correspondence to Sabesan Karuppiah, MD, MPH, at Reprints are not available from the authors.

Author disclosure: No relevant financial affiliations.


show all references

1. U.S. National Library of Medicine. DailyMed. Label: Xifaxan – rifaximin tablet. Updated November 1, 2015. Accessed December 6, 2016....

2. Pimentel M, et al. The effect of a nonabsorbed oral antibiotic (rifaximin) on the symptoms of the irritable bowel syndrome. Ann Intern Med. 2006;145(8):557–563.

3. Pimentel M, et al.; TARGET Study Group. Rifaximin therapy for patients with irritable bowel syndrome without constipation. N Engl J Med. 2011;364(1):22–32.

4. Menees S, Maneerattannaporn M, Kim HM, Chey WD. The efficacy and safety of rifaximin for the irritable bowel syndrome. Am J Gastroenterol. 2012;107(1):28–35.

STEPS new drug reviews cover Safety, Tolerability, Effectiveness, Price, and Simplicity. Each independent review is provided by authors who have no financial association with the drug manufacturer.

This series is coordinated by Allen F. Shaughnessy, PharmD, MMedEd, Contributing Editor.

A collection of STEPS published in AFP is available at



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