SIBO Antibiotics
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- Profile of rifaximin and its potential in the treatment of irritable bowel syndrome
- Rifaximin, gut microbes and mucosal inflammation: unraveling a complex relationship
- Rifaximin therapy for patients with irritable bowel syndrome without constipation
- Clinical trial: the combination of rifaximin with partially hydrolysed guar gum is more effective than rifaximin alone in eradicating small intestinal bacterial overgrowth
- Increased Incidence of Small Intestinal Bacterial Overgrowth During Proton Pump Inhibitor Therapy
- DDW: Traveler's Diarrhea Drug Eases IBS with Constipation
- A combination of rifaximin and neomycin is most effective in treating irritable bowel syndrome patients with methane on lactulose breath test
- Small intestinal bacterial overgrowth recurrence after antibiotic therapy
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Medically Reviewed By Oreoluwa Ogunyemi, MD & Written by Josh Sabourin, IBS Patient
A course of SIBO antibiotics is often one of the first recommendations from any gastroenterologist to treat SIBO.
This is because antibiotics are one of the quickest and most effective treatment options available for people suffering from SIBO or IBS.
But, there are things you NEED to know before proceeding with one of these treatment options.

In this article, we will break down everything you need to know about SIBO antibiotics including:
- How they work to treat SIBO and IBS
- Which antibiotics are used and what it means if they don’t work
- What Xifaxan is
- What you need to know about the treatment protocols before you proceed, so you can have the best outcome
Table of Contents
- 1 How Do Antibiotics Treat SIBO and IBS?
- 2 Xifaxan for SIBO and IBS
- 3 Xifaxan for IBS-D
- 4 Xifaxan for IBS and SIBO with Constipation
- 5 The Pros and Cons of Using Xifaxan for SIBO
- 6 Relapse Rates After SIBO Antibiotic Therapy
- 7 Why Does SIBO Relapse?
- 8 What Does it Mean if SIBO Antibiotics Don’t Work?
- 9 Can You Treat SIBO Without Antibiotics?
- 10 Concluding Thoughts on SIBO Antibiotics
How Do Antibiotics Treat SIBO and IBS?
First of all, if you don’t understand the basics of small intestine bacterial overgrowth which is found in 60-80% of people with IBS, I would recommend reading this article.
Basically, antibiotics treat SIBO by killing the overgrowth of bacteria in the small intestine.
Antibiotics do this by either stopping bacteria from replicating or destroying them. The reason we want to kill bacteria is that people with SIBO have accumulated too many bacteria in their small intestine (there should be much less) which cause debilitating digestive symptoms such as gas, bloating, diarrhea, constipation, fatigue, and abnormal stools.
When you treat this imbalance of bacteria in the small intestine with specific antibiotics, you reduce the amount of gas being produced, which can reduce symptoms.
For some people just treating this bacterial overgrowth can solve the problem, but others will need to address other underlying causes which enabled this bacterial overgrowth in the first place. (We will touch upon prevention later)
Xifaxan for SIBO and IBS
While there are a few different antibiotics usually prescribed to treat SIBO and IBS, the most common antibiotic is Xifaxan (Rifaximin).
Xifaxan is a non-systemically absorbed rifamycin with antimicrobial activity against gram-positive and gram-negative aerobic and anaerobic organisms.1
Xifaxan is used to treat traveler’s diarrhea, hepatic encephalopathy, IBS/SIBO, and a few other bowel infections.2
The main difference between Xifaxan and other SIBO antibiotics is that it is very minimally absorbed throughout the body and works specifically in the gastrointestinal tract.
This means that you are less likely to have toxic or systemic side effects compared to other antibiotics.
Also, the solubility of the drug increases 100-fold in the presence of bile acids (which are delivered directly to the small intestine after eating), meaning that its antimicrobial effect is much greater in the small bowel than in the colon.3
More so, Xifaxan decreases mucosal inflammation which is likely another reason it helps IBS patients. 4 Because of these properties, Xifaxan is a top antibiotic chosen for SIBO treatment.
Xifaxan for IBS-D
Xifaxan has been studied and used in all subsets of IBS and SIBO patients including diarrhea, constipation, and mixed type patients. But, it’s important to understand that there are differences in the study results when Xifaxan is given under different protocols for diarrhea and constipation type patients. In this section, we will go over Xifaxan’s use in IBS and SIBO patients with diarrhea specifically.
Xifaxan is one of the best antibiotics for SIBO and IBS with diarrhea.
In a number of different studies, it has been shown that a 2-week course of Xifaxan at a dose of 550 mg 3 times per day provides significant relief of IBS/SIBO symptoms, such as bloating, abdominal pain, and loose or watery stools.
The only thing you need to keep in mind when using antibiotics is that relapse can occur after treatment, so it’s vital to take preventative measures and continue to improve your overall digestive function.
That being said, using Xifaxan for SIBO in patients who have diarrhea as a predominant symptom is usually a very effective option.
Xifaxan Dosages for Diarrhea
- 1200 mg per day for 10 days with 5 g per day of partially hydrolyzed guar gum (source)
- 1650 mg per day for 14 days (source)
Xifaxan for IBS and SIBO with Constipation
Xifaxan is also used in constipation cases but there has been different research findings and outcomes using it with constipation.
It’s important to note that usually Xifaxan is used alone only in people with diarrhea or mixed type symptoms, whereas it is used in combination with other medications in constipation-predominant cases.
Despite this, there is some evidence that Xifaxan alone can help some people with constipation, such as this study.
As with all medical treatments, each person has a unique body and using Xifaxan alone for constipation may not be helpful for everyone. But, it has been reported that using Xifaxan in combination with Neomycin (rather then either alone) for constipation can be much more effective.
In this study, patients who tested positive for methane on the SIBO breath test (which usually indicates constipation type symptoms) were split into 3 groups. One group got Xifaxan alone, one just Neomycin, and the last group a combination of Xifaxan and Neomycin.
This table shows the results:
PROTOCOL | DOSAGE | METHANE ERADICATION |
Rifaximin + Neomycin |
1200 mg Rifaximin1000 mg Neomycin 10 days |
87% |
Neomycin Alone | 1000 mg Neomycin10 days | 33% |
Rifaximin Alone | 1200 mg Rifaximin10 days | 28% |
85% of patients getting combination treatment also noticed an improvement in their symptoms. These results show why Xifaxan alone is not the best option for those with constipation type symptoms; Xifaxan and neomycin work synergistically to treat different organisms in the gut, improving overall symptoms.
Xifaxan Combo Dosages for Constipation
- 1200 mg Rifaximin + 1000 mg Neomycin per day for 10 days (source)
- 1650 mg Rifaximin for 14 days + 1000 mg Neomycin for 10 days
The Pros and Cons of Using Xifaxan for SIBO
There are pros and cons when deciding to use SIBO antibiotics like Xifaxan.
Here is a list of both sides, so you can make the best decision possible
Pros:
- Works quickly when effective
- Protocols have been researched thoroughly
- One of the strongest treatment options
- Xifaxan is a non-absorbable antibiotic so it doesn’t cause as many systemic side effects
- Xifaxan can reduce mucosal inflammation
Cons:
- Xifaxan is very expensive, without insurance it usually costs around $1,500
- Xifaxan can still cause negative side effects (though it doesn’t happen as often since it acts mostly in the gut)
- You can still relapse after a successful treatment if there is a stubborn underlying cause
- Xifaxan isn’t as effective in constipation cases and needs to be combined with Neomycin
Relapse Rates After SIBO Antibiotic Therapy
I think it’s important to touch on the relapse rates after using antibiotics for SIBO. This helps you make the decision whether to try natural treatments initially or go straight to antibiotics, especially if you have to do multiple courses.
I think you will find that in the long run, it’s important to incorporate a mostly natural strategy, only using pharmaceuticals when your symptoms are very severe.
In this study, the aim was to investigate SIBO recurrence in patients after successful antibiotic treatment. They took 80 patients treated with Xifaxan and reassessed them 3, 6, and 9 months after their breath tests normalized. The results are informative and very important for people who use antibiotics to understand.
The Results:
- 3 months after successful antibiotic treatment 10 patients (10/80 or 12.6%) tested positive for SIBO again indicating relapse
- 6 months after successful antibiotic treatment 22 patients (22/80 or 27.5%) tested positive for SIBO
- 9 months after successful antibiotic treatment 35 patients (35/80 or 43.7%) tested positive for SIBO
They also showed that being older, having your appendix out, and chronically using proton pump inhibitors (like Prilosec) increased the chance of relapse. This means that if you have other health issues that are affecting your gut function you will be more likely to relapse and become a chronic SIBO patient.
This study is very important to understand; it shows that while antibiotics can definitely help a lot, they are only one helpful tool in the overall treatment strategy, and not a magic cure. In reality, many people deal with relapse and have to find a combination of strategies to help maintain their symptom relief while preventing recurrence.
Why Does SIBO Relapse?
This is a great question to ask any doctor or researcher who studies SIBO or IBS. There are many hypotheses right now but no final conclusion. Whoever figures out the solution to the relapse problem will be a rock-star! As mentioned above, SIBO is often a chronic condition, and like the study above showed, recurrence can occur even after a successful course of antibiotics.
It is thought the main reason recurrence occurs is that there is an underlying problem with gut function or the migrating motor complex (MMC).
Some patients who develop bacterial overgrowth have abnormal MMC, meaning that the waves that normally cleanse their small intestine are not effective. Therefore, they do not clear the bacteria and undigested materials as well as other people.
When these small intestine cleansing waves are damaged, it allows bacteria to accumulate, causing SIBO symptoms.
Some of the main prevention strategies which help SIBO patients are:
- Eating a healthy lower carbohydrate diet
- Prokinetic agents (natural or pharmaceutical)
- Fixing other issues that decrease gut motility
- Reducing stress and making healthy life changes (high stress can decrease motility)
What Does it Mean if SIBO Antibiotics Don’t Work?
While antibiotics are usually very effective for SIBO (at least in the short term), for others, they may not work at all or for only a very short period of time.
This can be very frustrating. So, what does this mean?
This can mean a few things:
- The SIBO antibiotic protocol was not appropriate for your specific gut bacteria
- You need an additional course of antibiotics or an elemental diet to treat your stubborn microbes
- You have developed antibiotic resistance, meaning the bacteria are not affected by the antibiotics
- You don’t really have SIBO, but instead a different type of gut dysbiosis or health issue
- If you relapse very quickly, you may need to focus on figuring out any underlying causes that may be contributing
Can You Treat SIBO Without Antibiotics?
This is an important question many people ask after looking at the SIBO antibiotic relapse rates, side effects, and the cost of purchasing Xifaxan. Yes, you can definitely treat SIBO without antibiotics and in many cases, this may be a better strategy over the long term.
When you realize that most people will relapse after a successful course of antibiotics it makes sense to consider treating SIBO naturally and taking a more gradual approach.
There are a few treatment options that you might find to be effective:
- Herbal antibiotics like Allimed, berberine, oregano oil, and neem
- Elemental diet protocol
- Long-term SIBO diet changes
- Probiotics
Remember that while some treatments work for others, they may not be the best for you. Everyone has a different health history and underlying causes contributing to their issues. It’s best to consult with a doctor for specialized advice.
Concluding Thoughts on SIBO Antibiotics
If you’re thinking about taking SIBO antibiotics like Xifaxan, know that they can work effectively and quickly. However, a course of Xifaxan is very expensive and you may still have side effects. Also, remember that there is a chance you may relapse once you stop taking the antibiotics.
If you are someone who is dealing with a stubborn case of SIBO- and willing to spend the money on Xifaxan- it can be a good option. On the other hand, if you don’t want to spend as much money and want to take a gentler long-term approach, using a natural treatment protocol may be your best bet. Using herbal antibiotics, the elemental diet or long-term diet changes can be just as effective as antibiotics.
If you want to review all the different treatment strategies used for SIBO before making a decision see this overview.
Thank you, just stumbled onto this today when wondering what I could eating wise to help myself when I finish taking
Xifaxan. I had no idea… You’ve given me a lot to look into, and I’m glad most of it is natural.
I find that probiotics help me. Does xifaxan kill good bacteria?
Most antibiotics kill both “good” and “bad” bacteria. It has been shown in studies that Xifaxan does not have systemic effects and acts only in the gut, so it does not do as much damage as a typical antibiotic. Some doctors consider it a ubiotic but personally I would still be careful with the side effects of using it too much.
I was just diagnosed with SIBO earlier today & filled my Xifaxan Rx. I’m slightly concerned after reading this page because my MD didn’t also recommend Neomycin, even though my problem has always (20+ years) been IBS-C. He did, however, recommend some specific pre- & probiotics. In any case…
I thought it might be helpful to others to know that there’s a coupon out there for Xifaxin. I’m so grateful to my pharmacist, who initially quoted $2000 for a non-covered, 2-week supply; she looked up a coupon, without prompting, that brought the Rx down to $728.
Elle,
Where did you get the coupon so others know where to get it?
It was the kind pharmacist who pulled it up on her computer, but I’m guessing she got it from here: https://www.xifaxan.com/hcp/he/access-and-savings
Is xifaxan safe for people w short bowel syndrome, specifically, 130cms, no colon and no ileum?
This is a question I would ask your doctor.
I’ve been on Xifaxan for over a week (550 mg 3/day) & have had no relief from my symptoms. Matter of fact, constipation has been worse. I have followed low FODMAP for 4.5 years & never been stricter than this past week (including recipes from Josh’s cookbook :->). Am I being impatient not giving the Xifaxin another week to take effect?
P.S. Thanks for this site! By far the most helpful resource out there since my SIBO Dx.
For constipation sometimes patients need XIfaxan + Neomycin or a combination protocol. Another product you can try to help reduce methane is Atrantil as well. A lot of times people who have problems with constipation need something to help reduce the methane gas which different organisms produce than the typical organisms that Xifaxan inhibits. In general, give your protocol the full chance to work but if it doesn’t work talk to your doctor about using something that can inhibit methane production if constipation is your predominant symptom.
Josh, I appreciate your responsiveness – thank you!
I’m just starting Xifaxin and Neomycin combination for a 2 week period but was advised not to do a Low Fodmap diet until I finished the course. This is because the antibiotics work best when the bacteria are well fed and growing actively. If the bacteria are starved of nutrients they go into a self protective mode which makes them less easy to kill. When we’re trying to get rid of these bugs it sounds counterproductive to feed them but if the end result is likely to be better, then that’s what I’m going to do. Following the antibiotics, I’ve also been advised to take Iberogast, a prokinetic, and to use betaine hydrochloride with pepsin, to acidify the stomach and help start protein digestion and then pancreatic digestive enzymes to help complete the digestive process. Hopefully this protocol will prevent SIBO returning. I tried Atrantil and Allicin Max for several months but while it helped, it wasn’t enough and my breath test results although slightly improved were still positive.
Sounds like a good plan! During treatment, it’s best not to be restrictive with your diet for the reasons you stated. Best of luck!
My sibo was diagnosed through a 3-hour glucose breath test. My doctor said I am hydrogen dominant sibo, and my methane levels were fine. This is confusing because I am not prone to diarrhea, but I AM prone to constipation.
So, she prescribed just the rifaximin for me, and not the neomycin.
My question is….should she have gone by my symptons (mild constipation) or by the test results? Should I have added the neomycin to the rifaximin?
It really just depends. If your doctor prescribed that protocol ask her why she did if you experience constipation. It’s better to have these talks with your doctor and to develop a relationship of trust so that you feel good going through with your treatments. Healing occurs when you trust your doctor and are working together to heal.
When you took that round of xifaxan and neomycin how did you feel while taking them and after taking them?
My gut felt great. If they are working effectively you should feel good and your stools should be normal. You may experience some side effects from the antibiotics like fatigue or mild flu-like symptoms during die-off, but your bowel symptoms should go away.
I’m 84&1/2 years old and have had Sibo for &1/2 years and initialy was treated with Neomycin 500mg twice, an antibiotic which worked for about 30 days each time. My current GI Dr wants me to go on Xifaxin which I have resisted and instead have been on a diet avoiding grains, sugar, etc and using homemade yogurt for about a year which has controlled the diarrhea but still have stomach discomfort. Should I consider Xifaxin?
I would consider Xifaxan if you have diarrhea.
Is it safe to try the natural remedies at the same time as the antibiotics?
I would do one or the other. Speak with your practitioner.
My daughter was diagnosed with SIBO and the insurance keeps denying Xifaxan, is this common? Just curious if this has happened to others often?
Yes, this is definitely common, unfortunately. I think it’s because it is mainly approved for travelers diarrhea and IBS-D specifically.