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Systematic (IUPAC) name
CAS number 80621-81-4
ATC code A07AA11 D06AX11
PubChem 6436173
DrugBank APRD01218
Chemical data
Formula C43H51N3O11 
Mol. mass 785.879 g/mol
Pharmacokinetic data
Bioavailability < 0.4%
Metabolism Hepatic
Half life 6 hours
Excretion Fecal (97%)
Therapeutic considerations
Pregnancy cat.


Legal status

Prescription only

Routes Oral

Rifaximin is a semisynthetic, rifamycin-based non-systemic antibiotic, meaning that the drug will not pass the gastrointestinal wall into the circulation as is common for other types of orally administered antibiotics. It is licensed for use to treat diarrhea caused by E. coli. It is not effective against Campylobacter jejuni, and there is no evidence of efficacy against Shigella or Salmonella species.

It may be efficacious in relieving chronic functional symptoms of bloating and flatulence that are common in irritable bowel syndrome.[1]

In 2005, it received orphan drug status for the treatment of hepatic encephalopathy.[2]

It is currently sold in the U.S. under the brand name Xifaxan by Salix Pharmaceuticals.

It's also sold in Europe under the name Spiraxin and Zaxine, both of which seem to be cheaper solutions. There isn't a generic version of the drug.


  1. ^ Sharara A, Aoun E, Abdul-Baki H, Mounzer R, Sidani S, ElHajj I. (2006). "A randomized double-blind placebo-controlled trial of rifaximin in patients with abdominal bloating and flatulence". Am J Gastroenterol 101 (2): 326.
  2. ^ Wolf, David C. (2007-01-09). Hepatic Encephalopathy. eMedicine. WebMD. Retrieved on 2007-02-15.
  • Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically. National Committee for Clinical Laboratory Standards, Sixth Edition, Wayne PA. — January 2003
  • Micromedex information on rifaximin
  • FDA label approved for Xifaxan (PDF warning)

This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Rifaximin". A list of authors is available in Wikipedia.
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