SIBO, Xifaxan, IBS, and the FDA


SIBO, Xifaxan, IBS and the FDA. Today I want to update you on the SIBO (small intestinal bacterial overgrowth) medication of choice. Just a reminder that I am not a medical doctor and do not prescribe medications. I am a clinical functional medicine nutritionist and so this is for information only.

SIBO, Xifaxan…What is Xifaxan?

Xifaxan also, known as Rifaximin, is an expensive antibiotic that runs over a thousand dollars per needed supplies for a 2-week treatment of SIBO. This is the antibiotic of choice for SIBO. The typical prescription is 550mg 3 x a day for 14 days. Originally, this medication was used for traveler’s diarrhea, stopping the symptoms in over 79% of patients. It then became very popular and effective in the treatment of SIBO, and that is probably how you have heard about it.

FDA Approval of Xifaxan for IBS…

Xifaxan has been approved by FDA for IBS-D (diarrhea) and you may have already seen their ads on television. I think we are the only country that allows the direct-to-consumer pharmaceutical advertisement….That is just my three cents…

Should Xifaxan and IBS be synonymous?

This is the point of this post. If you look at studies, a surprisingly high percentage of IBS-D may be post-infectious. And now we understand that it is not the food poisoning itself or the pathogen itself like Campylobacter that may be causing IBS but the toxins that these pathogens produce in the small intestine. HOWEVER, if you have IBS, do not automatically assume your IBS is infection-driven and requires Xifaxan. Do your due diligence. This is where it is a good idea to get evaluated by a functional medicine nutritionist or a clinical and experience licensed nutritionist AND an integrative gastroenterologist. All are hard to find, but you can look at the IFM website for some local practitioners understanding that you still have to ask around about their expertise. Sometimes IBS diarrhea is refractory and not caused by infection. It may be a side effect of a gallbladder removal or food sensitivity. There are many potential causes. Sometimes just a dwindling colonic microbiota is the culprit. The bottom line is: I have worked with many IBS patients over the years and everyone is different and has different root causes. You deserve to find out what is behind this, and so you need a proper evaluation!

IBS and SIBO..SIBO and IBS…a chicken and an egg???

People with IBS have a high risk of SIBO. Or also you can say that if you have SIBO, it may have been the reason why you have developed IBS or IBS-like symptoms. If you do have SIBO and want to get on Xifaxin, please test first. All you need to do is a breath test. It is noninvasive, quick, just uncomfortable because you will have drink a sugary solution (lactulose). The worst side effect will be some gas or bloating from it. But that is it. You definitely want to know if you have SIBO first before taking any antibiotic, even if it is Rifaximin. There are too few gastroenterologists that have the lab on site to do breath test. The good news is that there are two labs that provide breath test as a take-home kit, Genova and Commonwealth Labs. I have accounts with both of these labs just in case. So if you live in a remote area and would otherwise not be able to ever get this tested properly, I make sure I have it available.

How successful is Xifaxan if you do have SIBO?

Dr Mullin has done a study at Hopkins showing that herbal protocol is at least as successful short term and we need more studies on recurrent SIBO treatments. In the meantime, studies abound showing that Xifaxan is indeed the best medication for SIBO, with 72% patients responding to it over 18 weeks. The 36% in the study never relapsed. This means that 64% will not resolve SIBO after the first treatment. This is consistent with my experience with patients. Dr Pimentel’s patients’ range in the 30-70% ratio. I see that sometimes the medication is the best fit. Sometimes the herbal protocol is better. Sometimes patients start with one and have to move to the other or vice versa due to increased reactivity or lowered tolerance. As you can see, it is not a cure-all straight forward solution.

I am saying that so that you do not get discouraged if, after your 1st or 2nd round of Rifaximin, you only to drop numbers by 10-20% each time. That is more common than you think and you should expect it. I will have more posts on why this may be happening and what to do about it. If you treat it once and for all, that is fantastic. I still stress that you should work with a trained clinician experienced with SIBO so that you learn what to avoid in your case so that you do not relapse!!! SIBO can be very frustrating because recurrence is frequent.

If your breath test is positive for methane as well, Xifaxan is not sufficient, but that is a topic for another post!

In a Nutshell:

  • Work with someone experienced.
  • Get tested properly so you test and not guess.
  • Know the limitations of Rifaximin.
  • Understand the root causes of your SIBO infection and understand how to prevent recurrence in future.
  • If you are also positive for methane, Xifaxan will not be able to clear your SIBO alone.

Take care of yourself, until next time!!!

Kasia Kines

Note: What I did not mention in the video… diarrhea makes it difficult to get a reliable breath test reading. If the transit time is too fast, even if SIBO is present, there is not enough time for the bacteria to feed, and the result may be false negative.


No comments yet


The long-term health benefits, energy and nutrition education from the program more than pay for the cost of the class. The manual for the class would easily be a best seller if published~ Georgia