Xifaxan for SIBO

Treatment of SIBO involves eradication of excess bacteria and addressing any underlying conditions that lead to SIBO so that it doesn’t come back.

One way to eradicate excess bacteria is a drug called Xifaxan. So in this article, we’ll review what Xifaxan is, how it works, whether it’s effective for SIBO and if yes, how long do you have to take it.

Let’s get started!

What is Xifaxan?

Xifaxan is the trade name of a drug called rifaximin, which is a broad-spectrum, non-absorbable antibiotic used to treat GI conditions like traveler’s diarrhea, SIBO, and hepatic encephalopathy (where bacteria in the gut produce excess ammonia and lead to brain dysfunction).

Many doctors consider it as the drug-of-choice for eradicating bacterial overgrowth seen in SIBO. It’s so effective because the body can’t absorb it, which means it stays inside your gut for prolonged periods, enhancing bacterial killing.

The drug works by inhibiting an enzyme called RNA polymerase inside bacteria. Bacteria use this enzyme to make proteins. Since rifaximin inhibits RNA polymerase, bacteria can longer make vital proteins to survive.

Rifaximin’s effectiveness can be judged from this study, where it eradicated SIBO in 84% of the patients it was given to. This eradication was sustained for up to 10 weeks after the treatment.

How long do you have to take Xifaxan for SIBO?

Xifaxan is generally taken for 14 days for the treatment of SIBO. You’re usually prescribed 1650 mg per day, which comes down to three 550 mg tablets per day.

You should note that the dosage and time period of your rifaximin treatment might vary depending on your overall health, co-existing medical conditions, and any other drugs that you might take. So it’s important to consult a healthcare provider for safe and accurate dosing of Xifaxan.

Sometimes, your bacterial overgrowth might be composed of methane-secreting bugs called archaea. This is called intestinal methanogen overgrowth (IMO) and in this case, rifaximin alone is not enough to treat your SIBO.

If you have IMO, you’ll be given Xifaxan in combination with another drug called neomycin. Just like Xifaxan, neomycin is not absorbed by the body and stays in the gut. And it also works by inhibiting bacterial protein synthesis.
The dosage and length of this combination is:

  • Neomycin 500 mg twice daily for 14 days
  • Xifaxan 550 mg thrice daily for 14 days

Again, your actual dosage regimen might be different, so make sure to consult a doctor.

How to use Xifaxan?

Xifaxan is taken as a tablet via the mouth. It can be taken with or without food, and it’s a good idea to take the drug at the same time each day so you don’t forget about it.

It’s also important to keep taking Xifaxan (and neomycin) for as long as your doctor has prescribed them even if you feel better.

Stopping treatment earlier than prescribed or skipping doses can make bacteria resistant to Xifaxan, which means there’s a high chance your SIBO will return and will need a stronger antibiotic to treat.

What are the side effects of Xifaxan?

Since Xifaxan kills bacteria indiscriminately, even the good bacteria of your gut end up getting killed. This can lead to an infection with C.difficile, which is a bug that attacks the gut when its microbiota is disturbed.

A C.difficile infection usually leads to watery diarrhea and may be potentially serious, so if you suffer from persistent diarrhea and abdominal cramping with or without blood in your stool, contact your doctor straight away.

A C.difficile infection can occur while you’re taking Xifaxan or up to 2 months after your treatment has ended.

But remember that your doctor has prescribed you Xifaxan because its benefits outweigh the risks, so there’s usually nothing to worry about.

Other side effects of Xifaxan may include:

  • Nausea
  • Joint pain
  • Abdominal pain
  • Headache
  • Dizziness
  • A severe allergic reaction. This is very rare but is important to recognize because it can be fatal. If you experience difficulty breathing or swallowing, itching, swelling, or rash after taking Xifaxan, seek medical attention right away.

One way to avoid this allergic reaction is to tell your doctor if you’ve experienced a prior reaction to any of the following:

  • Rifabutin
  • Rifampin
  • Rifapentine

Ingredients found in Xifaxan capsules can also trigger an allergic reaction — you can ask your doctor or pharmacist to give you a list of ingredients so you can make sure you’re not allergic to any.

Are there any alternatives to Xifaxan for SIBO?

Yes, patients who can’t tolerate Xifaxan or don’t respond to it can try alternative ways to eradicate their bacterial overgrowth.

Your doctor might prescribe you a different antibiotic like trimethoprim-sulfamethoxazole and metronidazole, which have been shown to be effective against SIBO.

You also have the option of alternative medicine like herbal supplements. Although the use of herbal supplements to eradicate bacteria in SIBO is controversial, we do have evidence that they work (some studies have shown them to be even more effective than rifaximin!).

For example, in this study, SIBO patients were divided into two groups. One group received rifaximin while the other received a herbal antibacterial. The results showed that herbal therapy was able to eradicate bacterial overgrowth in 64% of its recipients while rifaximin worked in only 34% of the patients who received it.

There were also many side effects in the rifaximin group (compared to only a single case of diarrhea in the herbal therapy group).

Probiotics and a low-FODMAP diet have also been shown to treat SIBO but we need more large-scale studies before we can say anything definitive about them. You can still try discussing them with your doctor if you don’t want to go with Xifaxan.


Xifaxan is the trade name for rifaximin, which is a broad-spectrum antibiotic that’s considered to be the first-line treatment for SIBO. It’s usually prescribed for 14 days for SIBO treatment but your exact regimen might differ.

Some patients don’t tolerate the drug well and in those cases, alternative antibiotics, herbal therapy, probiotics, and a low-FODMAP diet can be considered.




Medically reviewed by Onikepe Adegbola, MD PhD

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