Rifaximin Is a Non-Absorbable Antibiotic That Works Locally in Your Gut

Rifaximin is a prescription antibiotic that fights bacterial infections in the intestines without being absorbed into your bloodstream.

Sold under the brand name Xifaxan, Rifaximin belongs to the rifamycin class of antibiotics. It's manufactured by Salix Pharmaceuticals, a subsidiary of Bausch Health. Unlike most antibiotics that travel throughout your body, Rifaximin stays in your gastrointestinal tract — less than 0.4% reaches your bloodstream. This makes it uniquely suited for treating gut-specific conditions.

Rifaximin is not a controlled substance.

What Is Rifaximin Used For?

Rifaximin has three FDA-approved uses:

1. Travelers' Diarrhea

Rifaximin treats travelers' diarrhea caused by noninvasive strains of E. coli in adults and children 12 and older. It's taken as 200 mg three times daily for 3 days.

2. Hepatic Encephalopathy

Rifaximin reduces the risk of overt hepatic encephalopathy (HE) recurrence in adults with liver disease. HE happens when a damaged liver can't clear toxins properly, leading to confusion, personality changes, and in severe cases, coma. Rifaximin works by reducing the gut bacteria that produce these toxins. The dose is 550 mg twice daily, taken on an ongoing basis.

3. Irritable Bowel Syndrome with Diarrhea (IBS-D)

Rifaximin treats IBS-D in adults. The dose is 550 mg three times daily for 14 days. Some patients need repeat courses if symptoms return.

Off-Label Uses

Doctors also prescribe Rifaximin off-label for:

• Small intestinal bacterial overgrowth (SIBO) — One of the most common off-label uses
• Clostridioides difficile infection — As an add-on to Vancomycin
• Inflammatory bowel disease
• Diverticular disease
• Rosacea associated with SIBO

How Is Rifaximin Taken?

Rifaximin comes in two tablet strengths:

• 200 mg tablet — Used for travelers' diarrhea
• 550 mg tablet — Used for hepatic encephalopathy and IBS-D

Key dosing details:

• Swallow tablets whole
• Can be taken with or without food
• For travelers' diarrhea: 200 mg three times daily for 3 days
• For hepatic encephalopathy: 550 mg twice daily (ongoing, do not stop without your doctor's approval)
• For IBS-D: 550 mg three times daily for 14 days

If you miss a dose, take it as soon as you remember. If it's almost time for your next dose, skip the missed dose and continue your regular schedule. Don't double up.

Who Should Not Take Rifaximin?

Do not take Rifaximin if you are:

• Allergic to Rifaximin or any rifamycin antibiotic — This includes Rifampin (Rifadin), Rifabutin (Mycobutin), and Rifapentine (Priftin)
• Pregnant or breastfeeding — Rifaximin is Pregnancy Category C. Animal studies showed potential fetal harm. Discuss risks with your doctor.

Use with caution if you have severe liver impairment (Child-Pugh Class C), as more of the drug may be absorbed into your bloodstream.

For a full list of drug interactions, see our guide on Rifaximin drug interactions.

How Much Does Rifaximin Cost?

Rifaximin is expensive. Here's the reality:

• Cash price: $1,800 to $2,400 for 60 tablets of 550 mg (a 30-day supply for hepatic encephalopathy)
• Generic available: No. A patent settlement with Teva delays generic entry until 2029.
• Insurance: Often covered but usually requires prior authorization and may require step therapy (trying Lactulose first for HE). Typically placed on Tier 3 or specialty tier.

Ways to save:

• Xifaxan Savings Card — Commercially insured patients may pay as little as $0-$75 per prescription. Visit xifaxan.com for details.
• Bausch Health Patient Assistance Program — For uninsured or underinsured patients
• Discount cards — Services like GoodRx, SingleCare, and others may help reduce your out-of-pocket cost

For a complete breakdown, read our guide on how to save money on Rifaximin.

Side Effects at a Glance

Common side effects include nausea, stomach pain, dizziness, fatigue, headache, and reddish urine (harmless). Serious but rare side effects include C. diff infection, drug-resistant superinfection, and severe allergic reactions. Rifaximin carries no boxed warning.

For the full breakdown, see our detailed guide on Rifaximin side effects.

Final Thoughts

Rifaximin is a unique antibiotic that works where you need it — in your gut — with minimal systemic side effects. It's a critical medication for hepatic encephalopathy, an effective treatment for IBS-D, and a go-to for travelers' diarrhea. The biggest downside is cost, but savings programs can help significantly.

If you need help finding Rifaximin at a pharmacy near you, Medfinder can show you which locations have it in stock right now.