What Is Rifaximin and How Does It Work?

Rifaximin is an antibiotic indicated for the treatment of patients 12 years of age and older with travelers' diarrhea caused by noninvasive strains of Escherichia coli (E. coli), and to lower the risk of worsened brain function, or hepatic encephalopathy, in adults with liver failure.

  • Rifaximin is available under the following different brand names: Xifaxan.

What Are Dosages of Rifaximin?

Dosages of Rifaximin:


  • 200mg
  • 550mg

Dosage Considerations – Should be Given as Follows:

Traveler's Diarrhea

  • Adult: 200 mg orally every 8 hours for 3 days
  • Children under 12 years: Safety and efficacy not established
  • Children 12 years and older: 200 mg orally every 8 hours for 3 days, with or without food

Hepatic Encephalopathy

  • Maintenance of remission
  • 550 mg orally every 12 hours

Irritable Bowel Syndrome

  • Indicated for irritable bowel syndrome with diarrhea (IBS-D) in adult men and women
  • 550 mg orally every 8 hours for 14 days; recurrence of symptoms can be retreated with a 14-day treatment course, up to 2 times
  • Available in a unit-dose package containing 42 tablets (i.e., 2 week supply) for this indication

What Are Side Effects Associated with Using Rifaximin?

Side effects of rifaximin include:

  • Gas (flatulence)
  • Headache
  • Feeling as if your bowels are not completely emptied
  • Feeling you need to urgently empty your bowels
  • Abdominal or stomach pain
  • Nausea
  • Constipation
  • Fever
  • Vomiting
  • Bloating
  • Dizziness
  • Tired feeling
  • Swelling in your hands, feet, or torso

Other side effects of rifaximin include:

  • Hypersensitivity reactions (including allergic dermatitis)
  • Itching
  • Rash
  • Serious side effects of rifaximin include:

    • Persistent diarrhea
    • Abdominal or stomach cramping
    • Blood or mucus in your stool

    This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Rifaximin?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

  • Rifaximin has no known severe interactions with other drugs.
  • Serious interactions of rifaximin include:
  • Rifaximin has moderate interactions with at least 59 different drugs.
  • Rifaximin has no known mild interactions with other drugs.

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns, or for more information about this medicine.

What Are Warnings and Precautions for Rifaximin?


  • This medication contains rifaximin. Do not take Xifaxan if you are allergic to rifaximin or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.


  • Hypersensitivity to rifamycin antibiotics

Effects of Drug Abuse

  • None

Short-Term Effects

  • See "What Are Side Effects Associated with Using Rifaximin?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Rifaximin?"


  • Not effective in diarrhea complicated by fever, hematochezia, or diarrhea due to pathogens other than Escherichia coli
  • Not effective against traveler's diarrhea due to Campylobacter jejuni
  • Clostridium difficile-associated diarrhea has been reported
  • Efficacy against traveler's diarrhea due to Shigella spp and Salmonella spp not proven
  • Discontinue if symptoms worsen or persist more than 24-48 hours
  • Possibility of pseudomembranous colitis
  • Monitor patients with severe hepatic impairment for increased systemic exposure
  • Coadministration with P-GP inhibitors substantially increases systemic exposure to rifaximin; coadministration of cyclosporine with rifaximin resulted in 83-fold and 124-fold increases in rifaximin mean Cmax and AUC in healthy subjects

Pregnancy and Lactation

  • Use rifaximin with caution during pregnancy if the benefits outweigh the risks. Animal studies show risk and human studies are not available or neither animal nor human studies were done
  • Do not use rifaximin if nursing or do not nurse
Medscape. Rifaximin.
RxList. Xifaxin.

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