Xifaxan dosage, forms, and strengths

Xifaxan is a brand-name prescription drug used to provide relief from the symptoms of irritable bowel syndrome with diarrhea (IBS-D), reduce the risk of symptomatic poisoning of the brain due to advanced liver disease (hepatic encephalopathy), and treat traveler’s diarrhea caused by noninvasive strains of E. coli. 

The active ingredient in Xifaxan is rifaximin, an oral antibiotic that works against a wide spectrum of bacteria. Rifaximin, however, is minimally absorbed and concentrates in the gastrointestinal tract, so it is primarily used to treat infections of the gut and liver. E. coli infection is one such bacterial gut infection, but both hepatic encephalopathy and IBS-D are associated with gut bacteria.

RELATED: What is Xifaxan? | Get Xifaxan discounts 

Xifaxan forms and strengths

Xifaxan tablets come in two dose strengths:

• Tablets: 200 milligrams (mg), 550 mg

Source: Epocrates

Xifaxan dosage for adults

Xifaxan, a non-absorbable oral antibiotic, is FDA approved to treat traveler’s diarrhea caused by E. coli bacteria, help relieve the symptoms of irritable bowel syndrome with diarrhea (IBS-D), and help prevent overt hepatic encephalopathy. Some healthcare providers may prescribe Xifaxan off-label to treat recurrent Clostridium difficile infection, active Crohn’s disease, small intestinal bacterial overgrowth (SIBO), or to prevent traveler’s diarrhea.

Source: Epocrates, Xifaxan HCP website, Prescriber’s Digital Reference

Xifaxan dosage for treatment of irritable bowel syndrome with diarrhea (IBS-D)

Salix Pharmaceuticals, the manufacturer of Xifaxan, primarily markets the drug to consumers as a treatment to reduce the symptoms of irritable bowel syndrome with diarrhea. IBS is characterized by a host of symptoms such as abdominal pain, diarrhea, and constipation, with no discernible cause. An imbalance between good and harmful bacteria in the colon, called gut dysbiosis, is associated with some of these symptoms. Xifaxan is taken for two weeks to alter the bacterial environment in the colon to prevent abdominal pain and diarrhea, two symptoms closely linked to bacterial overgrowth. In clinical trials, people taking Xifaxan experienced anywhere from six weeks to six months of relief from abdominal pain and diarrhea. In these patients, the median symptom-free period was ten weeks. If IBS symptoms recur, the Xifaxan two-week dosage regimen can be repeated up to two more times. 

• Standard dosage for symptom relief of irritable bowel syndrome with diarrhea: 550 mg tablet taken three times per day for 14 days

• Maximum dosage for irritable bowel syndrome with diarrhea: 1650 mg per day

Xifaxan dosage for hepatic encephalopathy

Xifaxan is FDA-approved as an add-on treatment to prevent overt hepatic encephalopathy (HE), a neurological/psychiatric complication of severe liver disease. The symptoms of hepatic encephalopathy, ranging from slight neurological deficits in the mildest cases to coma in the worst, are due to a buildup of toxins in the brain, toxins that a healthy liver normally cleans out of the bloodstream. Covert (“hidden”) HE is characterized by mild symptoms, but overt (“open”) HE has significant clinical symptoms such as lethargy, personality changes, confusion, abnormal behavior, or tremor.

In HE, the primary culprit in poisoning the brain is ammonia, a compound normally broken down by the liver. Gut bacteria produce much of the ammonia that ends up in the blood. Xifaxan is given to reduce ammonia produced by gut bacteria activity when a person is at risk for hepatic encephalopathy. Patients taking Xifaxan will take other drugs such as lactulose (to reduce ammonia in the blood), l-ornithine/l-aspartate (to increase the amount of ammonia converted into urea), and zinc. Xifaxan treatment will persist for as long as hepatic encephalopathy is a risk.

• Standard dosage for prevention of hepatic encephalopathy: 550 mg tablet taken twice per day as long as the patient is at risk for overt HE

• Standard dosage for prevention of hepatic encephalopathy: 1100 mg per day

Xifaxan dosage for treatment of traveler’s diarrhea due to

Xifaxan is FDA approved to treat traveler’s diarrhea due to infection by noninvasive strains of Escherichia coli as long as there are no complications such as fever or blood in the stools. Traveler’s diarrhea is a common medical condition experienced by up to half or more of people who travel to resource-limited areas. Many types of microbes can be the culprit, including bacteria, viruses, or parasites. However, Escherichia coli, a type of bacteria, is the most common cause, responsible for around 30% of all cases. For cases caused by other pathogens, Xifaxan is not an appropriate treatment for traveler’s diarrhea. 

To treat the underlying E. coli infection, a healthcare professional will prescribe a low dose of Xifaxan three times a day for three days.

• Standard dosage for treatment of uncomplicated traveler’s diarrhea due to noninvasive E. coli infection: 200 mg tablet taken three times a day for three days

• Maximum dosage for treatment of uncomplicated traveler’s diarrhea due to noninvasive E. coli infection: 600 mg per day

Xifaxan dosage for children

Xifaxan is FDA approved for use in adolescents 12 years of age and older for the treatment of traveler’s diarrhea due to noninvasive strains of E. coli. However, some healthcare providers may prescribe Xifaxan off-label as an add-on treatment for recurrent C. difficile infections. Because very little rifaximin, the active ingredient in Xifaxan, is absorbed into the bloodstream, dose reductions are not necessary for younger patients.

• Standard dosage for treatment of uncomplicated traveler’s diarrhea due to E. coli infection in children 12 years of age and older: 200 mg tablet taken three times a day for three days

• Maximum dosage for treatment of uncomplicated traveler’s diarrhea due to E. coli infection in children 12 years of age and older: 600 mg per day

Source: Epocrates

Xifaxan dosage restrictions

The only contraindications to Xifaxan use are allergies to rifaximin or any drug in the rifamycin family. People with severe liver disease (Child-Pugh class C) can take the drug at recommended doses but will require close monitoring. People with kidney impairment can take Xifaxan at normal doses if approved by their doctor, but specific guidelines are not available.

Xifaxan dosage for pets

Xifaxan is not FDA approved for use in animals, however, veterinarians may use it off-label to treat chronic diarrhea (chronic enteropathy, the animal version of irritable bowel syndrome) in dogs or to prevent or relieve neurological problems caused by liver disease (hepatic encephalopathy) in dogs and cats. Doses for animals have not been standardized, so doses may vary by practitioner. Never give Xifaxan to a pet, unless prescribed by the pet’s veterinarian.

How to take Xifaxan

Xifaxan is prescribed in only one dosage form: tablets. People on Xifaxan will take a single tablet two or three times a day with or without food.

• Follow the prescribing directions carefully.

• The medicine is taken two or three times a day. Follow the daily dosing schedule on the prescription label.

• Use this medicine for the full-time prescribed. Even if symptoms get better, continue to take the medicine until the end of the treatment period. Stopping this medication early not only decreases its chances of success but also increases the likelihood of growing bacteria resistant to antibacterial drugs.

• Store Xifaxan at room temperature (59˚ to 77˚F) protected from heat and light. Keep out of the reach of children and pets.

Xifaxan dosage FAQs

What happens if I miss a dose of Xifaxan?

If a dose is missed, take it as soon as possible. However, skip the missed dose if it is almost time for the next dose. Do not take extra medicine to make up for a missed dose.

How do I stop taking Xifaxan?

Xifaxan can be discontinued at any time without causing problems. Do not, however, stop taking Xifaxan until directed by the prescribing healthcare professional, even if symptoms improve.

Some people, however, may need to stop taking Xifaxan before the treatment period is up. Anyone who has a hypersensitivity reaction will be immediately taken off Xifaxan. Other people may be taken off Xifaxan if they have serious adverse reactions like C. difficile- associated diarrhea (CDAD) or C. difficile colitis. Other people may want to stop taking Xifaxan because common adverse effects of rifaximin such as swelling in the extremities (peripheral edema), abdominal swelling (ascites), or headache are too hard to live with. If so, only stop Xifaxan under the medical advice of a healthcare professional.

Can you overdose on Xifaxan?

If too much Xifaxan is taken, call a poison helpline or get medical advice from a healthcare professional. However, an overdose of Xifaxan is not expected to do much. In double-blind clinical trials, people who took too much Xifaxan had the same side effects as people taking a placebo.

What interacts with Xifaxan?

Unlike other antibiotics, Xifaxan has only a few drug interactions. That’s because almost none of the drug is absorbed into the body. Even so, it is always a good idea to have a list of all prescription drugs, over-the-counter medicines, and vitamins or supplements that are regularly taken to share with the doctor and the pharmacist when getting a prescription. This is the best way to avoid possible side effects due to drug interactions.

Xifaxan’s most worrisome drug interactions are with a family of drugs called P-glycoprotein (P-gp) inhibitors such as cyclosporine. The combination raises the risks of Xifaxan side effects. P-gp inhibitors are unfamiliar to most people, but healthcare professionals know them well and will be careful about combining them with Xifaxan. 

Is it safe to take Xifaxan during pregnancy?

Women who are pregnant may not be prescribed Xifaxan in the first trimester because animal studies showed an increase in birth defects. However, Xifaxan can be prescribed in the second and third trimesters under close supervision of the healthcare provider.

There are no studies on whether Xifaxan affects lactation or is safe to take while breastfeeding. Because so little of the drug is absorbed into the body, healthcare providers believe nursing infants will have little exposure to the drug.

Related resources for Xifaxan dosages:

• Antibiotics for the treatment of irritable bowel syndrome, Gastroenterology & Hepatology

• Escherichia coli, StatPearls

• Hepatic encephalopathy, StatPearls

• Hepatic encephalopathy diagnosis and treatment, Neurology Compendium

• Rifaximin, Drugs and Lactation Database

• Rifaximin, Plumb’s Drug Summaries

• Rifaximin, StatPearls

• Rifaximin drug summary, Prescribers’ Digital Reference

• Traveler’s diarrhea, StatPearls

• Veterinarians: New options for chronic diarrhea, Animal Biome

• Xifaxan, Epocrates

• Xifaxan HCP, Salix Pharmaceuticals

• Xifaxan prescribing information, DailyMed