rifaximin, Xifaxan

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GENERIC NAME: rifaximin


DRUG CLASS AND MECHANISM: 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.



PREPARATIONS: Tablets: 200 and 550 mg

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

PRESCRIBED FOR: Rifaximin is approved for treating patients 12 years or older with traveler's diarrhea caused by Escherichia coli. It also is effective at preventing traveler's diarrhea. It is approved for preventing the recurrence of hepatic encephalopathy in individuals 18 years of age or older. Rifaximin also has been shown to effectively treat non-constipating irritable bowel syndrome.

DOSING: 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.

DRUG INTERACTIONS: 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.

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

NURSING MOTHERS: It is not known whether rifaximin is excreted in breast milk.

SIDE EFFECTS: Common side effects associated with rifaximin include nausea, vomiting, constipation, urge to defecate, dizziness, fatigue, headache, abdominal pain, fever, flatulence, and fluid retention (edema). 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.

REFERENCE: FDA Prescribing information for Xifaxan

Last Editorial Review: 2/11/2011 2:41:00 PM

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