Rifaximin

Pronunciation: rif-AX-i-min.

Generic name: rifaximin
Brand names: XIFAXAN, Targaxan, Xifaxanta
Drug class: Rifamycin antibacterial (minimally absorbed, gut-selective)
Form: Film-coated tablet, 200 mg or 550 mg depending on indication and country product
Route: Oral
Legal status: Prescription-only medicine

Supply Rules Vary

Trade names by country: United States · United Kingdom · Canada · Australia

Australia: XIFAXAN (5) (6) · Full directory

What rifaximin is and how it works

Rifaximin is an orally taken rifamycin antibiotic that is minimally absorbed into the bloodstream and acts mainly within the gut. Its approved uses differ sharply by tablet strength and country: 200 mg tablets treat travelers' diarrhoea caused by certain non-invasive strains of E. coli; 550 mg tablets reduce the recurrence of episodes of overt hepatic encephalopathy, and in the United States are also approved to treat irritable bowel syndrome with diarrhoea (IBS-D) in adults. (1) (2) (3) (4)

The exact approved use depends on the tablet strength, the diagnosis, and the country-specific product label. Rifaximin will not work for diarrhoea that is bloody or accompanied by fever, or for diarrhoea not caused by a susceptible organism, and is not a general-purpose antibiotic for any gut infection.

Mechanism of action: how rifaximin works

Rifaximin is a semisynthetic rifamycin derivative that binds the beta-subunit of bacterial DNA-dependent RNA polymerase, inhibiting bacterial RNA synthesis. Its extremely low oral bioavailability (under about 0.4%) concentrates its antibacterial effect within the gastrointestinal tract with minimal systemic exposure in patients with normal hepatic function. (1) (3)

What rifaximin is used for

Travelers' diarrhoea (200 mg tablets)

Used to treat travelers' diarrhoea caused by non-invasive strains of E. coli. In the United States this is approved for adults and children 12 years of age and older; the UK Xifaxanta 200 mg product's safety and efficacy have not been established in patients under 18. It does not treat diarrhoea that is bloody, accompanied by fever, or caused by other pathogens, and must not be used for more than 3 days or for a repeat course without medical reassessment. (1) (2) (4)

Reduction in recurrence of hepatic encephalopathy (550 mg tablets)

Used long-term in adults to reduce the risk of overt hepatic encephalopathy recurring in people with advanced liver disease. This is not a treatment for an acute hepatic encephalopathy episode itself and is typically prescribed and monitored by a specialist. (1) (3)

Irritable bowel syndrome with diarrhoea (550 mg tablets) — United States only

In the United States, 550 mg rifaximin is also approved to treat IBS-D in adults. This indication is not part of the current UK or Australian product labels reviewed for this page; do not present it as a general or global use. (1) (2)

Before taking rifaximin

Do not take / not appropriate for

Do not take rifaximin if you have had a hypersensitivity reaction to rifaximin, or to another rifamycin antibiotic such as rifampicin or rifabutin. (all products) (1) (3) (4)
The UK Targaxan (550 mg) label additionally lists intestinal obstruction as a contraindication. (Targaxan 550 mg (UK)) (3)

Tell your clinician about

Any known allergy to rifaximin or to other rifamycin-class antibiotics (rifampicin, rifabutin, rifapentine).
Liver disease, especially advanced or severe (Child-Pugh Class C) impairment, because systemic exposure to rifaximin rises substantially in this group.
Whether current diarrhoea is bloody or accompanied by fever, or has not improved, before starting or continuing treatment for travelers' diarrhoea.
All current medicines, especially ciclosporin or other P-glycoprotein inhibitors, and warfarin.
Pregnancy, plans for pregnancy, or breastfeeding.

(1) (2) (3) (4)

How to take rifaximin

Rifaximin is taken by mouth, with or without food, exactly as prescribed for the specific indication and tablet strength.
Dosing schedules differ by indication: travelers' diarrhoea uses a fixed short course (not exceeding 3 days, with no repeat course); hepatic encephalopathy recurrence reduction is typically long-term twice-daily treatment; the US IBS-D indication uses a fixed multi-week course that a prescriber may authorise to repeat if symptoms recur.
Do not change the dose, tablet strength, frequency, or course length yourself, and do not use a tablet strength prescribed for one indication to treat a different condition.

(1) (2) (3) (4)

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)

Missed dose

Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue the regular dosing schedule. Do not take a double dose to make up for a missed one. If you are unsure, ask your pharmacist or prescriber.

Overdose

If more than the prescribed amount may have been taken, contact a poison control service or emergency department. In the United States call 1-800-222-1222 or use poisonhelp.org; call emergency services immediately for collapse, seizures, or unresponsiveness. (2)

Side effects

Common effects differ somewhat by indication. Some effects, such as severe diarrhoea appearing during or after treatment, need prompt medical attention rather than self-management.

Nausea, stomach discomfort, or flatulence

What to notice: Mild digestive upset is commonly reported, particularly with the travelers'-diarrhoea course.

What to do: Tell the prescriber if severe, persistent, or worsening. (4) (2)

Dizziness, tiredness, or headache

What to notice: Reported with both travelers'-diarrhoea and long-term hepatic-encephalopathy courses.

What to do: Discuss persistent or troublesome symptoms with the prescribing clinician. (4) (2)

Joint pain or muscle tightening

What to notice: Reported more often with longer courses.

What to do: Tell the prescribing clinician if troublesome. (2)

Clostridioides difficile-associated diarrhoea (CDAD)

What to notice: Watery or bloody diarrhoea, often with stomach cramps and fever, which can occur during treatment or for up to 2 months afterward.

What to do: Contact the prescribing clinician promptly for assessment; do not treat new diarrhoea yourself with an antidiarrhoeal medicine without medical advice, because this can be a sign of a different, antibiotic-associated condition. (2) (1)

Severe skin reaction

What to notice: Skin blistering or peeling, mouth ulcers, or fever, which can indicate a rare severe cutaneous reaction (including Stevens-Johnson syndrome or toxic epidermal necrolysis).

What to do: Seek urgent medical care if these symptoms occur; a clinician or emergency service will decide whether rifaximin needs to be stopped. (3)

Serious warnings

Clostridioides difficile-associated diarrhoea — urgent

Symptoms: Watery or bloody diarrhoea, abdominal cramping, and fever, developing during treatment or up to about 2 months after finishing it.

Action: Contact the prescribing clinician promptly. This can occur with almost any antibacterial medicine and needs medical assessment rather than self-treatment. (2) (1)

Severe hypersensitivity reaction — emergency

Symptoms: Hives, rash, swelling of the face, throat, or tongue, difficulty breathing or swallowing, or hoarseness.

Action: Seek emergency medical care immediately. (2) (1)

Severe cutaneous adverse reaction — urgent

Symptoms: Skin blistering or peeling, mouth or genital sores, fever, or widespread rash.

Action: Get urgent medical care immediately; a clinician or emergency service will decide whether rifaximin needs to be stopped; this can rarely indicate Stevens-Johnson syndrome or toxic epidermal necrolysis. (3)

Interactions

Medicine or test	Effect	Action
Ciclosporin and other P-glycoprotein inhibitors	Can substantially increase systemic exposure to rifaximin (studies have shown roughly 80- to 124-fold increases with ciclosporin), raising the chance of exposure-related side effects.	The prescriber and pharmacist should review all current medicines before rifaximin is started; do not combine without specialist advice. (1) (3)
Warfarin	Changes in INR (both increases and decreases) have been reported in people taking warfarin with rifaximin.	Clinicians should monitor INR closely when starting or stopping rifaximin in a patient taking warfarin, and adjust the warfarin dose as needed. (1) (3)
Other rifamycin-class antibiotics	Cross-hypersensitivity is possible with other rifamycins such as rifampicin, rifabutin, and rifapentine.	Tell the prescriber about any known rifamycin allergy before starting rifaximin. (1) (3)

Pregnancy, breastfeeding, kidney/liver function, age

Severe hepatic impairment

In people with severe liver impairment (Child-Pugh Class C), systemic absorption of rifaximin can rise substantially. Rifaximin for hepatic encephalopathy is prescribed for people with advanced liver disease specifically because of this population's needs, so a specialist should monitor treatment and adjust the plan for the individual's exact liver-disease severity. (1) (3)

Pregnancy

Use in pregnancy is not routinely recommended as a precaution; animal studies at high exposure showed some effects. Discuss the balance of benefits and risks with the prescriber if pregnant or planning pregnancy. (3) (1)

Breastfeeding

Whether rifaximin passes into breast milk in clinically relevant amounts is not well established. Discuss with the prescriber whether to continue breastfeeding or treatment. (1)

Children and adolescents

Age criteria differ by country and product. In the United States, the 200 mg travelers'-diarrhoea indication is approved from age 12; the UK Xifaxanta 200 mg product's safety and efficacy have not been established in patients under 18. Hepatic encephalopathy and IBS-D indications are limited to adults on the sources reviewed for this page. (1) (4)

Monitoring

Before starting

Confirm the exact diagnosis, the correct tablet strength for that indication, and the country-specific product label.
Assess liver disease severity, rifamycin allergy history, pregnancy/breastfeeding status, and all current medicines, especially ciclosporin and warfarin.
Confirm that current diarrhoea, where relevant, is not bloody or accompanied by fever before treating with the travelers'-diarrhoea course.

During treatment

Watch for new or worsening diarrhoea, fever, or abdominal cramping that could indicate Clostridioides difficile-associated diarrhoea.
Monitor INR in patients taking warfarin.
Reassess hepatic-encephalopathy symptom control periodically for people on long-term treatment.
Do not authorise a repeat travelers'-diarrhoea course without medical reassessment.

(1) (3) (4)

Storage

Keep tablets in their original container, tightly closed, at room temperature and away from excess heat and moisture (not in a bathroom). Keep out of reach of children, and dispose of unused medicine through a pharmacy take-back programme rather than flushing it.

Study the drug class: Rifamycins

Professional information

Clinician-facing context only. Use the current local indication, dosing table, hepatic-impairment guidance, and monitoring protocol for the exact tablet strength and product.

All regions

Indication: Any rifaximin use

Dose summary: No universal dose is displayed. Dose, course length, and repeat-course eligibility depend on the exact indication, tablet strength, age, and current local product information.

Renal context: Rifaximin is minimally absorbed; renal-impairment-specific dosing has not been established in the sources reviewed. Severe hepatic impairment (Child-Pugh C) substantially increases systemic exposure and requires individual specialist assessment. (1) (3)

Mechanism of action

Hepatic guidance

Systemic exposure increases substantially in severe hepatic impairment (Child-Pugh Class C); use local product information and specialist judgement rather than a web-based adjustment.

Overdose note

Reported experience with rifaximin overdose is limited given its low systemic absorption; manage supportively and involve a poison-information service or specialist as needed. (1) (3)

Frequently asked questions

Can I use rifaximin for any type of diarrhoea?

No. Rifaximin is not effective for diarrhoea that is bloody or accompanied by fever, or for diarrhoea caused by organisms other than non-invasive E. coli. It is not a general-purpose antidiarrhoeal antibiotic. (1) (2)

How long can I take rifaximin for travelers' diarrhoea?

The travelers'-diarrhoea course must not exceed 3 days, even if symptoms continue, and a second course should not be taken without medical reassessment. (4) (1)

Are the 200 mg and 550 mg rifaximin tablets interchangeable?

No. They are approved for different indications and should only be used exactly as prescribed for the specific condition being treated. (1) (3) (4)

Is rifaximin approved for IBS-D outside the United States?

The UK and Australian product information reviewed for this page does not include an IBS-D indication; this use is specific to the current US label. (1) (3)

What is the mechanism of action of rifaximin?

What is the generic name of Rifaximin?

The generic name is rifaximin. It is sold under brand names including XIFAXAN, Targaxan, Xifaxanta. (1) (2) (3) (4)

What class of drug is rifaximin?

Rifaximin is classed as: Rifamycin antibacterial (minimally absorbed, gut-selective). (1) (2) (3) (4)

References

XIFAXAN (rifaximin) tablets, for oral use — full prescribing informationU.S. Food and Drug Administration · United States · dated 2023 · accessed 2026-07-23 · source 1
Rifaximin: MedlinePlus Drug InformationMedlinePlus, U.S. National Library of Medicine · United States · accessed 2026-07-23 · source 2
Targaxan 550 mg film-coated tablets — Summary of Product Characteristicselectronic Medicines Compendium (UK) · United Kingdom · accessed 2026-07-23 · source 3
Xifaxanta 200 mg Film-coated Tablets — Summary of Product Characteristicselectronic Medicines Compendium (UK) · United Kingdom · accessed 2026-07-23 · source 4
XIFAXAN rifaximin 550 mg tablet blister pack — ARTG entry 183411Therapeutic Goods Administration (TGA) · Australia · accessed 2026-07-23 · source 5
XIFAXAN rifaximin 200 mg film-coated tablet blister pack — ARTG entry 222643Therapeutic Goods Administration (TGA) · Australia · accessed 2026-07-23 · source 6

Brand names by country

Single-ingredient rifaximin names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

XIFAXAN550 mg, 200 mg · salix pharmaceuticals, inc.

United Kingdom

Targaxan (3)current licensed product · 550 mg · Norgine Pharmaceuticals Limited
Xifaxanta (4)current licensed product · 200 mg · See current UK product information

Canada

ZAXINE

Australia

XIFAXAN (5) (6)current register product example · 550 mg, 200 mg · Norgine Pty Ltd

View brands in additional countries.