Does Rifaximin Treat IBS? Yes, Here’s How.

There are many therapies that exist for the management of IBS including diet, supplements, medications, and more. One option gaining more attention in the IBS community is an antibiotic medication called rifaximin. But does rifaximin treat IBS? As a dietitian specializing in irritable bowel syndrome, I always encourage patients to learn about the ‘why’ behind the therapies they choose and this medication is no different. Let’s review how rifaximin helps to manage IBS by understanding what it does, who would benefit most, potential side effects, and more.

Table of Contents

1. What is rifaximin?
2. What is rifaximin used for?
3. How does rifaximin work?
4. How is rifaximin different from other antibiotics?
5. What does a typical rifaximin treatment for IBS look like?
6. Does rifaximin cause side effects?
7. Who is most likely to benefit from rifaximin treatment?
8. What to eat while taking rifaximin
9. Summary: Does rifaximin treat IBS?

What is rifaximin?

Rifaximin is a type of broad spectrum antibiotic used to treat a variety of conditions.¹ ² ³ It can be found under trade names such as Xifaxan, Zaxine, Xifaxanta, and Normix. 

What is rifaximin used for?

Rifaximin is approved for use in certain conditions. Most commonly it is used to treat hepatic encephalopathy, however it is now commonly used to manage diarrhea predominant IBS, as well as treat SIBO. 

Hepatic Encephalopathy 

Hepatic encephalopathy occurs in individuals with severe liver disease. As liver function decreases, it has a difficult time clearing toxins as it usually would. These toxins can then build up in the blood and affect brain function causing cognitive impairment. Rifaximin has been used to decrease the quantity of toxins produced in the gut due to bacterial overgrowth, therefore reducing the symptoms associated with decreased liver function.¹ 

IBS

Irritable bowel syndrome is a disorder of the gut brain axis This means that the digestive system isn’t functioning properly but there is nothing structurally wrong with it. Based on the current research, treatment of irritable bowel syndrome with rifaximin is only indicated for those with diarrhea predominant IBS.³ ⁴ ⁵

SIBO

SIBO stands for Small Intestine Bacterial Overgrowth. It is a disorder where increased bacteria are seen in the small bowel. In high numbers, these bacteria disrupt normal digestion by fermenting carbohydrates and other substances, and causing a low level inflammatory response in the gut. This leads to a variety of GI symptoms including bloating, diarrhea, abdominal pain, and nausea. Rifaximin works in the small intestine to reduce total bacterial load and resolve symptoms.³ 

Traveler’s Diarrhea

Traveler’s diarrhea occurs when an individual consumes contaminated food or water and results in loose stools, abdominal cramping and pain. It most typically results from E. coli contamination, but can also be related to other contaminants.  Rifaximin works to target and kill the pathogenic bacteria to resolve symptoms.¹

Now let’s get into the basics of using rifaximin to treat IBS.

How does rifaximin work?

Antibiotics are a group of medications which target and kill unwanted bacteria. Many types of antibiotics work on one specific type of bacteria, however rifaximin is a broad spectrum antibiotic. This means that rifaximin can target and kill a wide variety of unwanted bacteria rather than only one or two specific types. It works by disrupting the way that harmful bacteria reproduce, limiting the extent to which they can cause disease. Additionally, rifaximin reduces inflammation in the GI tract and has a positive benefit on the gut’s natural microbiota.¹ ² While rifaximin does kill off harmful bacteria like all antibiotics are designed to do, there are a few ways in which it differs from other antibiotics as well.

How is rifaximin different from other antibiotics?

Rifaximin is a non-systemic, non-absorbable antibiotic.³ ⁴ This means it stays localized in the digestive system and does not get absorbed into the bloodstream unlike many other antibiotics. Rifaximin is inactivated by bile acids before reaching the colon, so it does not have antimicrobial effects on our gut microbiota (which is primarily found in the colon).¹ ⁶ It may also have eubiotic (beneficial) effects on our colon’s microbiota which additionally may help manage IBS symptoms. ¹ ²

Additionally, research has shown that rifaximin is not associated with the development of antibiotic resistance and has no correlation to clostridium difficile (C. diff) infection.¹ ³ Therefore, in comparison to typical antibiotic treatment, rifaximin treatment is quite low risk.

What does a typical rifaximin treatment for IBS look like?

A typical course of rifaximin is administered in a dose of 550 mg, three times per day over 14 days though your physician may prescribe a different dose or length of treatment.⁴

Multiple treatments for both IBS and SIBO are common. Studies show that approximately half of IBS-D patients with SIBO experience relapse within one year of rifaximin treatment. However, approximately one third of them did not experience any symptom recurrence in the 2 years following treatment.⁶ Participants were not followed beyond two years, so additional research is still needed to determine the rate of recurrence on a longer timeline.

Research on the appropriate length of treatment indicated for IBS and SIBO patients is still expanding to determine the best length of treatment with the lowest chance of symptom recurrence. 

Does rifaximin cause side effects?

Yes, side effects may occur with rifaximin treatment, however they are often less intense than other antibiotic treatments.³ ⁵ Flatulence is commonly reported alongside headache, nausea, abdominal pain, bowel urgency and rectal tenesmus, the feeling of needing to pass stool even when empty.⁵ ⁷ Since rifaximin is poorly absorbed and stays localized in the digestive tract, systemic side effects are rare. 

Who is most likely to benefit from rifaximin treatment?

Rifaximin treatment for IBS is indicated for individuals with IBS-D with no constipation and individuals with SIBO.⁴ 

Did you know that approximately 30% of people with IBS will test positive for SIBO? With many overlapping signs and symptoms, this is not surprising.

SIBO is more common in IBS patients than healthy individuals and should be considered in IBS-D patients who do not respond adequately to diet and lifestyle changes. 

Since multiple rounds of rifaximin may be necessary, and with rifaximin being an expensive drug, we often advocate for patients to receive a hydrogen and methane breath test (HMBT), a test used to diagnose SIBO, prior to considering rifaximin for IBS-D. Why? 

Studies show that 60% of individuals with a positive breath test for SIBO result have been shown to respond to rifaximin treatment.⁶ However, 26% of patients who tested negative to the hydrogen and methane breath test also responded to treatment.⁶ This finding is likely due to HMBT being an imperfect test, as well as breath testing being unable to pick up certain types of SIBO. Prior to starting rifaximin treatment, a breath test may be indicated to predict if antibiotic treatment is likely to help treat symptoms. Talk to your gastroenterologist to discuss if a breath test prior to rifaximin treatment may be the best option for you.

What to Eat While Taking Rifaximin

Rifaximin can be taken with or without food.⁷ At this point, there are no diet recommendations for while taking rifaximin to improve its efficacy. You may be following a specialized diet to manage your IBS symptoms – this is something that can continue throughout treatment unless other recommendations are provided by your health care team. 

Does rifaximin treat IBS?

Yes, rifaximin has been shown to improve symptoms in patients with IBS.⁴ There is strong research to support the use of rifaximin in IBS-D, however it is not yet applicable to other subtypes of IBS. The success in IBS-D patients on rifaximin treatment may be connected to underlying SIBO. 

Discuss your treatment options with a gastroenterologist, if possible, and inquire if a hydrogen and methane breath test may be beneficial to predict if rifaximin could work for you. Work with a dietitian to better understand the best ways for you to manage your IBS.