Rifaximin

A poorly absorbed (gut-acting) antibiotic of the rifamycin family

Rifaximin is available under several brand names depending on the country. Ask your pharmacist for the product available to you.

Most antibiotics are absorbed into the blood and act throughout the body. Rifaximin is absorbed only in very small amounts, so it stays mostly in the gut, where it changes the balance of the bacteria that live there. In liver disease, some gut bacteria produce substances, such as ammonia, that can reach the brain when the liver cannot clear them and cause confusion (hepatic encephalopathy). By reducing these bacteria, rifaximin lowers the load of these substances. In other conditions it reduces the gut bacteria thought to cause bloating, gas and diarrhea.

Take rifaximin exactly as your doctor prescribes: the amount, the number of times a day and the length of treatment are decided for your condition and are not the same for everyone. It is taken by mouth and can be taken with or without food. When used to prevent hepatic encephalopathy it is usually a long-term medicine and should not be stopped on your own, even if you feel well. If you miss a dose, take the next dose at the usual time and do not double up; ask your pharmacist if unsure.

• Swelling of the face, lips or throat, difficulty breathing, hives or a widespread rash — May be a serious allergic reaction. Stop the medicine and seek emergency care immediately.

• Severe, watery or bloody diarrhea that does not stop, with belly cramps or fever — Antibiotics can allow a bowel infection called Clostridioides difficile to grow. Contact your doctor urgently or go to the emergency department.

• Worsening confusion, extreme sleepiness, or fainting — May be hepatic encephalopathy getting worse or another illness. This needs urgent medical assessment.

• Fever, chills or new belly pain and swelling — May be an infection in someone with liver disease. Seek medical care the same day.

• Yellow skin or eyes, dark urine or severe tiredness — May show your liver disease is worsening. Contact your doctor promptly.

Tell your doctor and pharmacist about all medicines you take. Some medicines, such as cyclosporine and certain medicines that affect drug transporters in the gut, can raise rifaximin levels in the blood, and rifaximin may affect some medicines such as warfarin (blood thinner), so blood tests may be needed. Rifaximin may reduce how well some oral birth control pills work in some people, so ask about extra contraception. Do not take it if you are allergic to rifaximin or other rifamycin antibiotics.

Your doctor will follow your symptoms, mental state, liver and kidney blood tests and, if you take blood thinners such as warfarin, clotting tests. Tell your doctor if you develop new diarrhea while on treatment.

Do not stop rifaximin on your own, particularly if you take it to prevent hepatic encephalopathy, since stopping may allow confusion to come back. Stop and seek emergency care only for signs of a severe allergic reaction, and call your doctor if you have severe diarrhea or other serious side effects. Your doctor decides if and when treatment can stop or be changed.

There is limited information about the use of rifaximin in pregnancy and breastfeeding. Tell your doctor if you are pregnant, planning pregnancy or breastfeeding so that benefits and risks can be weighed. Do not start or stop it without medical advice.

• Why am I taking rifaximin, and for how long?

• Do I need to take lactulose as well?

• Is it safe with my other medicines, including blood thinners?

• What should I do if I get diarrhea or confusion?

• How will you check that it is working?

This guide comes from the Saudi Gastroenterology Association (SGA) patient library, prepared by the Approved for publication by SGA; individual clinician review is ongoing. Last reviewed: 2026-04-24. It is for education and does not replace your doctor's advice.