Rifaximin: Uses, How It Works, Dosing and Safety

Rifaximin is an antibiotic you probably haven’t heard much about—until you needed it. It stays in the gut, so it treats infections in the intestines without much getting into your bloodstream. That makes it useful for a few specific conditions: traveler’s diarrhea, some cases of IBS with diarrhea (IBS‑D), and preventing episodes of hepatic encephalopathy in people with liver disease.

What rifaximin treats and how it works

For traveler’s diarrhea caused by noninvasive E. coli, rifaximin can clear symptoms quickly. For IBS‑D, a short course can reduce stool frequency and urgency for weeks. In hepatic encephalopathy, rifaximin lowers gut bacteria that produce ammonia, which helps reduce episodes of confusion related to liver failure. Mechanically, it blocks bacterial RNA synthesis in the gut. Because it’s poorly absorbed, its effects stay local and systemic side effects are fewer than with many other antibiotics.

Not every gut infection needs rifaximin. It won’t work for invasive infections or those caused by organisms outside the intestines. Your doctor will decide if it’s the right choice based on your symptoms and tests.

Dosing basics and practical tips

Typical doses vary by condition. For traveler’s diarrhea, common dosing is 200 mg three times a day for three days. For IBS‑D, many studies use 550 mg three times a day for 14 days, sometimes repeating if symptoms return. To prevent hepatic encephalopathy, the standard is 550 mg twice a day long term. These are general ranges—always follow your prescriber’s instructions.

Take rifaximin with or without food, at roughly the same times each day. Don’t stop early just because you feel better; stopping too soon might let symptoms return. If you miss a dose, take it when you remember unless it’s near the next dose—don’t double up.

Store the pills at room temperature and keep them dry. If you have liver disease, diabetes, or are pregnant or breastfeeding, tell your doctor before starting rifaximin. While absorption is low, decisions must be individualized.

Side effects are usually mild—nausea, headache, constipation, or stomach pain. Serious allergic reactions are rare but seek help if you get hives, swelling, or trouble breathing. Like all antibiotics, rifaximin can change gut flora and in rare cases contribute to C. difficile infection. Report severe diarrhea or fever right away.

Buying and safety: rifaximin is prescription-only in most places. Use licensed pharmacies and avoid unverified online sellers. If cost is a concern, ask your provider about generics, patient assistance, or approved alternatives. Avoid unnecessary antibiotic use—overuse fuels resistance and harms long-term gut health.

If you’re considering rifaximin, bring a clear list of symptoms, current meds, and medical history to your appointment. That helps your clinician choose the right treatment and dosing for you.