Rifaximin — Compare Prices at US & Canada Pharmacies

Rifaximin belongs to the anti-infective agents - misc. class of antibiotics. WHO classifies it as an 'Watch' antibiotic under its AWaRe stewardship framework.

Rifaximin is FDA-approved for traveler's diarrhea caused by non-invasive strains of E. coli — the most common cause of the condition — in adults and children 12 and older. Because it stays almost entirely in the gut rather than entering the bloodstream, it can clear this specific type of E. coli without the broader side-effect exposure of a systemic antibiotic.

The standard course is short: 200 mg three times a day for 3 days. It's not a preventive medication taken before or during travel in the way some people assume — it's meant to treat diarrhea once it starts. It's also not effective for every cause of traveler's diarrhea; it doesn't cover invasive bacteria that cause fever or bloody stools, so if you develop those symptoms while traveling, that's a sign to see a doctor rather than rely on rifaximin alone.

In people with advanced liver disease, the liver can lose its ability to clear certain toxins — ammonia in particular — that are normally produced by bacteria in the gut. When those toxins build up, they can affect brain function, causing confusion, personality changes, disrupted sleep, and in severe cases, a decreased level of consciousness. This is called hepatic encephalopathy, and it can come and go in episodes.

Rifaximin is used to reduce how often these episodes recur, by reducing the population of ammonia-producing bacteria in the gut. It's typically taken twice daily, on an ongoing basis rather than as a short course, often alongside lactulose (a laxative that also helps clear ammonia from the gut) — the two are frequently used together rather than as alternatives to each other. This is a genuinely serious condition managed by a hepatologist or gastroenterologist as part of a broader liver disease care plan, and rifaximin's role here is specifically about reducing recurrence, not treating an acute episode in progress — a sudden change in mental status in someone with liver disease needs prompt medical evaluation regardless of what maintenance medication they're on.

Rifaximin is approved for irritable bowel syndrome with diarrhea, a condition where imbalances in gut bacteria are thought to contribute to symptoms like abdominal pain, bloating, and loose stools. Unlike the ongoing use for hepatic encephalopathy, IBS-D treatment is a defined 14-day course.

Because IBS-D symptoms can return after the antibiotic effect wears off, rifaximin is sometimes repeated — the FDA approval allows for up to two additional 14-day courses if symptoms recur, spaced out from the first course. It's not a cure for IBS-D and doesn't work for everyone; if it doesn't meaningfully help after a course, your provider will typically move on to a different approach rather than repeating it indefinitely. It's specifically for the diarrhea-predominant subtype of IBS — it isn't used for IBS with constipation.

Xifaxan has long been one of the pricier oral antibiotics, and cost is a genuinely common complaint about it. A large part of the reason is that it was, for many years, only available as the brand-name product — patent and market exclusivity protections kept generic versions off the market well after many other drugs of its era had gone generic, which is part of why the price stayed high for so long.

Generic rifaximin has more recently become available, which is typically the single biggest lever for lowering the cost — ask your pharmacist whether a generic is available and being used for your prescription, since brand-name Xifaxan can still be dispensed by default in some cases. Manufacturer patient-assistance programs have also historically been used for this drug given its cost, particularly for the ongoing hepatic encephalopathy indication — it's worth asking your provider's office or the manufacturer directly whether one currently applies to your situation, since these programs change over time.

Take rifaximin exactly as prescribed for your specific condition — the dose, frequency, and course length differ meaningfully between traveler's diarrhea, hepatic encephalopathy, and IBS-D, so don't assume a leftover prescription from one use is appropriate for a different reason to take it. It can be taken with or without food.

Tell your provider about your complete medical history before starting, particularly any liver disease more advanced than mild (severe liver impairment can allow more of the drug to reach the bloodstream than intended, raising side-effect risk) and any medications you take, especially cyclosporine or other drugs that strongly affect a transporter protein called P-glycoprotein, which can also increase how much rifaximin is absorbed systemically. Contact your provider if diarrhea doesn't improve, comes with fever or blood in the stool, or if you develop signs of an allergic reaction.