What is rifaximin, and how does it work (mechanism of action)?


Rifaximin is a semi-synthetic antibiotic used for treating traveler’s diarrhea and hepatic encephalopathy. It is derived from rifamycin, a naturally occurring chemical produced by a bacterium called Streptomyces mediterranei. Rifaximin is active against Escherichia coli bacterial strains that cause traveler’s diarrhea, preventing growth of the bacteria by preventing them from manufacturing proteins needed for their replication and survival. By suppressing growth of the bacteria, rifaximin reduces symptoms of traveler’s diarrhea. Hepatic encephalopathy is a serious neurologic complication of advanced liver disease that affects the brain. It is believed to be caused by the absorption of ammonia and other chemicals produced by bacteria in the intestine. It is believed that rifaximin prevents and treats hepatic encephalopathy by reducing the intestinal bacteria that produce ammonia. The FDA approved rifaximin in May 2004.

What brand names are available for rifaximin?


Is rifaximin available as a generic drug?


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Do I need a prescription for rifaximin?


What are the side effects of rifaximin?

Common side effects associated with rifaximin include:

Many of these side effects are also symptoms of traveler’s diarrhea which rifaximin is used for treating. Rifaximin also causes allergic reactions, rash, and itching. Like other antibiotics rifaximin can alter the normal bacteria in the colon and encourage overgrowth of some bacteria such as Clostridium difficile which causes inflammation of the colon (pseudomembranous colitis). Patients who develop signs of pseudomembranous colitis after starting rifaximin (diarrhea, fever, abdominal pain, and possibly shock,) should contact their physician immediately.


What is the dosage for rifaximin?

The recommended dose for traveler’s diarrhea is 200 mg 3 times daily for 3 days and the recommended dose for hepatic encephalopathy is 550 mg twice daily. Rifaximin may be administered with or without meals.

Which drugs or supplements interact with rifaximin?

Rifaximin does not interact with oral contraceptives and does not significantly interact with midazolam. Rifaximin has a low risk of drug interactions because it is poorly absorbed into the blood stream, and it does not significantly affect liver enzymes that break down most drugs.

Is rifaximin safe to take if I’m pregnant or breastfeeding?

The safety of rifaximin in pregnant women has not been adequately evaluated.

It is not known whether rifaximin is excreted in breast milk.

What else should I know about rifaximin?

What preparations of rifaximin are available?

Tablets: 200 and 550 mg

How should I keep rifaximin stored?

Rifaximin should be stored at room temperature at 15 C – 30 C (59 F – 86 F).

Medically Reviewed on 3/19/2019


Medically reviewed by John P. Cunha, DO, FACOEP; Board Certified Emergency Medicine


FDA Prescribing information for Xifaxan