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Treatment > Medications

Rifaximin - Help with irritable bowel syndrome and bacterial overgrowth in the small intestine?

Dr. med. André Sommer

Dr. med. André Sommer

Rifaximin is an antibiotic that is taken orally, remains in the intestine and is not absorbed into the body. While in the intestine, it can kill bacteria and is therefore approved for the treatment of traveler's diarrhea, for example. A possible therapeutic effect on irritable bowel syndrome without constipation and bacterial overgrowth in the small intestine has also been discussed. Details are explained in the following text.

What is Rifaximin?

Rifaximin is an antibiotic. It inhibits the protein biosynthesis of the bacteria and in doing so kills them. The special thing about Rifaximin is that when it is ingested through the mouth, it remains completely in the intestine and is not absorbed at all into the body circulation through the intestinal mucosa or only one percent is absorbed. As a result, there are no systemic side effects that are otherwise common with antibiotics. However, it only works against bacteria within the intestine. The antibiotic effects of Rifaximin are locally limited, but include a large number of bacteria, which is why Rifaximin is considered a broad-spectrum antibiotic.

What diseases is Rifaximin used for?

In Germany, Rifaximin is approved for traveler's diarrhea, which is largely caused by certain strains of Escherichia coli. However, this does not apply to invasive diarrhea associated with fever or blood in the stool. Another indication for the antibiotic is the prevention of hepatic encephalopathy, a brain disease that is triggered by a liver dysfunction.

The drug has already been approved for other uses in other countries. These include:

  • Small intestine bacterial overgrowth (SIBO),
  • Diverticular disease,
  • Decontamination of the intestine before surgery,
  • Therapy for pseudomembranous colitis (by C. difficile).

With pseudomembranous colitis, intensive antibiotic therapy kills the physiological intestinal bacteria and leads to an excessive increase in the intestinal pathogen Clostridium difficile. This causes inflammation of the colon with fibrin deposits in the intestinal mucosa and severe diarrhea are the result. In some cases, stopping the antibiotic is sufficient as a therapy for pseudomembranous colitis. If not, other antibiotics effective against clostridia such as metronidazole or vancomycin have to be used - Rifaximin is also a possible alternative to these active ingredients. So far, multi-resistant Staphylococcus aureus (MRSA) is sensitive to Rifaximin, but this can of course change depending on use development of resistance.

How does Rifaximin affect the intestinal flora?

It has long been assumed that irritable bowel syndrome is due to an imbalance in the intestinal bacteria. This can happen, for example, after a gastrointestinal infection or after taking antibiotics for a long time. With this assumption as a basis, there are therapeutic approaches to introduce "healthy" bacteria into the intestine (e.g. via probiotics or fecal microbiotat transplantation, also known as stool transplantation) or to remove "disease-causing" bacteria from the intestine. The drug Rifaximin was also discussed in this context because its broad effectiveness could kill many different intestinal bacteria and at the same time it has little side effects due to the reduced absorption in the body.

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What effect does Rifaximin have on irritable bowel syndrome?

In 2011, two studies were published that were commissioned by the Rifaximin manufacturer Salix Pharmaceuticals to test the effect of Rifaximin on irritable bowel syndrome. A total of 1,260 patients with irritable bowel syndrome without constipation were examined.

  • Rifaxamin group: A total of 1,260 patients with irritable bowel syndrome without constipation were examined.
  • Placebo group The other group took an inactive placebo preparation instead.
  • The participants did not know whether they were in the antibiotic or placebo group and were asked about their symptoms after the treatment.

In the Rifaximin group, around 41 percent of the subjects reported an improvement in their symptoms - but also in the placebo group, at least around 31 percent claimed this. The symptoms of “flatulence” and “feeling of fullness” improved, which could be due to the fact that bacteria are responsible for the additional gas development and were killed by the antibiotic. These differences could still be demonstrated after ten weeks, even if the symptoms returned in some of the subjects from both groups. The effect was statistically significant and, accordingly, not only attributable to chance.

How should Rifaximin be used in irritable bowel syndrome?

In fact, these studies also raise the question of whether the differences are clinically relevant, i.e. whether an individual with irritable bowel syndrome would actually benefit from Rifaximin and feel a noticeable improvement. The published study assessed the medicinal effect as clinically relevant, while, for example, the trade journal "Der Arzneimittelbrief" came to the opposite result and advised against antibiotic administration with irritable bowel syndrome. Due to these ambiguities, the high financial costs of the therapy and the lack of further independent studies that examine the influence of Rifaximin on irritable bowel syndrome, the drug has not yet been approved for this indication in Germany.

What are the side effects of Rifaximin?

Because Rifaximin is hardly absorbed into the body's circulation, systemic side effects and interactions with other medications are negligible. Like placebo supplements, the medication caused some people to experience the following:

  • Stomach pain
  • Bloating
  • Cramps
  • Nausea

Rifaximin should not be used for bloody diarrhea because larger amounts of the antibiotic can pass into the body and the effects of it are not known. There is also insufficient data to predict how Rifaximin will work in children and the elderly. So far, attempts to change the intestinal flora (microbiome) of a person through interventions have been very experimental. It has not been finally clarified which bacterial mixtures represent the ideal intestinal flora and how they could be specifically selected. Manipulation of the intestinal flora with antibiotics is always associated with the risk of provoking other diseases, such as pseudomembranous colitis.

Does Rifaximin lead to resistance development?

Another concern when using Rifaximin too often or too widely is the development of resistance. This means that bacteria could learn to defend themselves against the remedy and as a result can no longer be treated with it. Rifaximin is related to the antibiotic Rifampicin, which is an important drug in tuberculosis treatment - developing resistance to similar antibiotics could therefore be fatal. For this reason too, the responsible authorities are currently refraining from recommending the treatment of irritable bowel syndrome with Rifaximin: Giving the medication to millions of people affected could very quickly lead to the development of resistance in intestinal bacteria without the patients experiencing sufficient advantage from the treatment.

P. Leyer et al. S3-Leitlinie Reizdarmsyndrom: Definition, Pathophysiologie, Diagnostik und Therapie. Gemeinsame Leitlinie der Deutschen Gesellschaft für Verdauungs-und Stoffwechselkrankheiten (DGVS) und der Deutschen Gesellschaft für Neurogastroenterologie und Motilität (DGNM). 2011, Online:, downloaded on 04/07/2016
M. Pimentel et al. Rifaximin therapy for patients with irritable bowel syndrome without constipation. New england journal of medicine, 2011, 364.1, p. 22-32. Online:, downloaded on 04/07/2016
Rifaximin ist keine gute Wahl beim Reizdarm-Syndrom. Der Arzneimittelbrief, 2011, 45.14a Online at,45,14a_2366.pdf, downloaded on 04/07/2016
H. S. Füeßl: Rifaximin beim Colon irritabile auch wiederholt effektiv. MMW - Fortschritte der Medizin, 2012, 154.6, p. 46. Online: downloaded on 04/07/2016

Dr. med. André Sommer

Dr. med. André Sommer

I’m André, a medical doctor from Berlin. Together with a team of medical doctors, nutritionists and data scientists we empower people to understand digestive issues with our app Cara Care.

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