What Is Rifaximin Used For?

Aden | 05 Dec 2025

Rifaximin has become one of those medications people start hearing about more once they get into the world of digestive issues. A lot of folks first come across it when their doctor brings up IBS, especially IBS-D, and suddenly this antibiotic shows up in the conversation even though it doesn’t act like the traditional antibiotics used for sinus infections or pneumonia. Rifaximin works in a very different way — almost entirely inside the gut — which is probably why it’s grown so much in popularity these past years. Doctors like using something that helps without flooding the whole body, and patients usually handle it pretty well.

It’s also kind of interesting that people tend to think of it only as an “IBS antibiotic,” but rifaximin actually has a few separate identities depending on the dose and the condition being treated.

What Rifaximin Actually Is

Rifaximin is an antibiotic, yes, but not the kind that spreads through your bloodstream. It stays mostly in the intestine, barely getting absorbed at all. That’s what makes it different from the usual antibiotics people take for infections. Most of them enter the bloodstream and travel everywhere. Rifaximin basically sits right where the problem is — the gut — and does its job without affecting the rest of the body very much.

This low absorption is one of the reasons doctors feel more comfortable using it for chronic digestive conditions. It doesn’t hit the liver or kidneys the way other meds might, and because it doesn’t circulate widely, it tends to have fewer of the old-school antibiotic side effects.

How Rifaximin Works in the Body

Rifaximin reduces certain bacteria that live in the intestines — not wiping everything out, but lowering the excess that contributes to symptoms like bloating, loose stools, pain, or even the toxin buildup seen in liver disease. Its effect is pretty local. It calms things down in the gut, which can create a noticeable shift in digestion for the people who respond well to it.

Because it stays inside the intestine, rifaximin helps restore balance without disturbing the whole system. This is probably why patients often tolerate rifaximin 550 mg or other doses more easily compared to medicines that circulate throughout the body.

Main Conditions Rifaximin Is Used For

IBS-D (Irritable Bowel Syndrome with Diarrhea)

This is the use people know best. Rifaximin helps reduce:

• urgency

• bloating

• cramping

• watery or frequent stools

For some people, rifaximin gives weeks or months of relief. It’s not usually a permanent fix, but many patients describe it as a break from symptoms.

Traveler’s Diarrhea

If someone picks up E. coli while traveling, rifaximin can help shorten the illness. This use tends to be short-term and straightforward.

Hepatic Encephalopathy (HE)

This is a much more serious condition. People with advanced liver disease can build up toxins that affect the brain. Rifaximin helps lower those gut toxins, and when used together with lactulose, it helps keep patients more stable. This is often a long-term therapy and where rifaximin 550 mg is commonly used.

Additional Off-Label Uses

Doctors sometimes use rifaximin in situations that aren’t officially approved but make sense based on how the drug behaves.

• Small intestinal bacterial overgrowth (SIBO) is probably the most talked-about one.

• recurrent bloating

• certain chronic digestive conditions

• sometimes combined with other antibiotics for stubborn SIBO cases

These aren’t formal FDA-approved uses, but many specialists rely on rifaximin because it tends to work without causing widespread side effects.

Why Doctors Choose Rifaximin Over Other Antibiotics

A big reason is safety. Since rifaximin stays in the gut, it:

• has fewer interactions

• doesn’t disturb the gut microbiome as harshly

• doesn’t usually cause yeast infections or major GI upset

• can be repeated in several courses if symptoms return

Rifaximin is one of the only antibiotics where long-term or repeat therapy is considered fairly safe for certain conditions.

How Long Rifaximin Takes to Work

It depends on why you’re taking it.

• IBS-D: changes usually start around week one, sometimes week two

• Traveler’s diarrhea: relief can show up in 24–48 hours

• Hepatic encephalopathy: it works more like maintenance — keeping symptoms from worsening over time

Some people feel nothing for a few days and then suddenly notice their digestion is calmer.

Who Should Avoid or Be Cautious With Rifaximin

Even though rifaximin is pretty safe, a few groups need caution:

• people with severe liver impairment

• patients allergic to rifamycin drugs (like rifampin)

• anyone who needs treatment for infections outside the gut — rifaximin won’t work for those

It isn’t designed to treat sinus infections, pneumonia, UTIs, or anything outside the intestines because it never really enters the bloodstream.

Common Side Effects (Usually Mild)

Most people don’t experience much trouble with rifaximin side effects, but occasionally they notice:

• mild stomach discomfort

• gas or bloating

• headache

• fatigue

Since the medication doesn’t travel everywhere in the body, side effects tend to be less intense compared to older antibiotics.

Drug Interactions

Rifaximin doesn’t interact with many medications, but there are still things to stay aware of, especially in patients with hepatic encephalopathy who may be taking multiple drugs. And anyone with a rifamycin allergy shouldn’t use it.

Rifaximin in Long-Term Gut Conditions

IBS-D can be stubborn. That’s why rifaximin sometimes needs repeat courses. The gut bacteria rebalance for a period, and then symptoms return. When that happens, many providers will pair medication with lifestyle adjustments — things like a low-FODMAP diet or changes in fiber intake.

Questions People Commonly Ask

Does rifaximin cure IBS-D permanently?
No, but it can offer very meaningful breaks from symptoms.

Can I drink alcohol?
Moderate drinking usually isn’t a major issue, but heavy drinking can worsen digestive symptoms.

Why is rifaximin so expensive?
Because it’s a brand-name medication in many countries. Costs vary depending on availability and the version — like rifagut, rifagut 550, rifagut 400, or rifagut 200 in some markets.

Is it safe to repeat it more than once a year?
Often yes, depending on the condition. Doctors repeat it for IBS-D and SIBO fairly often.

Does it help constipation-type IBS?
Not usually. It’s mostly for diarrhea-predominant IBS.

Patient Tips From a Pharmacy Perspective

• take it exactly as your doctor outlines

• don’t skip doses; it weakens the effect

• finish the full course

• track your symptoms after the treatment — it helps guide future decisions

• ask your pharmacist how it fits with your other medications

Pharmacists often catch small details that make the treatment smoother.

Closing Thoughts

Rifaximin is unusual — in a good way. It’s an antibiotic designed mainly to work inside the gut, not all over the body. That makes it incredibly useful for certain gut disorders like IBS-D, traveler’s diarrhea, and hepatic encephalopathy. It’s one of the few antibiotics that can help with problems that aren’t classic infections, which is why doctors rely on it so much.

If someone is unsure whether rifaximin is the right fit, a pharmacist can walk through the symptoms, the dose, and possible alternatives. With conditions like IBS-D or SIBO, that guidance makes a big difference in how well the treatment works.