Rifagut 400: Uses, Benefits, Dosage And Side Effects

Digestive symptoms such as diarrhoea, bloating and abdominal pain can have several causes. Treatment depends on whether the problem is due to an infection, Irritable Bowel Syndrome, liver disease or another digestive condition.

Rifagut 400 is a prescription antibiotic containing rifaximin. It acts mainly inside your intestines and may be prescribed for selected gut-related conditions. However, it is not suitable for every type of diarrhoea or stomach problem.

You should take Rifagut 400 only after a doctor has assessed your symptoms. Do not use leftover antibiotics or follow another person's prescription.

What Is Rifagut 400?

Rifagut 400 is a brand of rifaximin. Each Rifagut 400 tablet contains 400 mg of rifaximin as its active ingredient.

Rifaximin belongs to the rifamycin class of antibiotics. Unlike many antibiotics that are absorbed into the bloodstream, rifaximin is poorly absorbed and remains largely within the digestive tract.

This gut-selective action allows the medicine to affect certain intestinal bacteria while limiting exposure throughout the rest of your body. However, side effects and drug interactions can still occur.

The conditions approved for a rifaximin product can vary according to its strength and local prescribing information. Your doctor will decide whether Rifagut 400 is appropriate for your particular diagnosis.

Composition And Drug Class Of Rifagut 400

The main details include:

• Active ingredient: Rifaximin
• Strength: 400 mg
• Dosage form: Oral tablet
• Drug class: Rifamycin antibacterial medicine
• Action: Suppresses susceptible bacteria within the intestines

Inactive tablet ingredients may differ. Check the product leaflet and tell your doctor if you have a known allergy to any medicine or tablet ingredient.

How Does Rifagut 400 Work?

Bacteria need to produce RNA and proteins to grow and survive. Rifaximin attaches to an enzyme called bacterial DNA-dependent RNA polymerase. This interferes with bacterial RNA production and stops susceptible bacteria from multiplying.

Because very little rifaximin normally enters your bloodstream, its activity is concentrated mainly in your intestines.

This does not mean that Rifagut 400 removes all intestinal bacteria. It affects particular susceptible organisms. It should therefore be used only when your doctor believes the expected benefit is greater than the risks.

Benefits Of Rifagut 400

Depending on your diagnosis, the potential benefits of Rifagut 400 may include:

• Reducing the growth of certain harmful intestinal bacteria
• Improving selected cases of bacterial diarrhoea
• Reducing bloating, loose stools and abdominal pain in some people with IBS-D
• Helping prevent recurrent hepatic encephalopathy in people with advanced liver disease
• Treating selected cases of suspected or confirmed small intestinal bacterial overgrowth
• Acting mainly in the gut with limited absorption into the bloodstream

The medicine will not provide the same benefit for every person. Your response depends on the condition being treated, the cause of your symptoms and the prescribed dosage.

Rifagut 400 Uses

Traveller's Diarrhoea

Rifaximin can be used for traveller's diarrhoea caused by susceptible, non-invasive strains of Escherichia coli.

It should not be used to self-treat diarrhoea accompanied by:

• Fever
• Blood in your stools
• Black stools
• Severe abdominal pain
• Repeated vomiting
• Marked weakness
• Signs of dehydration

These symptoms may indicate an invasive infection or another condition requiring different treatment.

Consult a doctor if diarrhoea becomes worse or does not start improving within 24 to 48 hours of treatment.

Irritable Bowel Syndrome With Diarrhoea

Rifaximin may be prescribed to adults with Irritable Bowel Syndrome with diarrhoea, commonly called IBS-D. It may help improve:

• Frequent loose stools
• Bloating
• Abdominal pain
• Urgency
• Overall IBS symptoms

IBS-D is not simply an infection. Rifaximin is thought to influence intestinal bacteria and other gut processes involved in symptoms.

Your doctor should first assess whether your symptoms fit IBS-D and whether further investigations are needed. Conditions such as coeliac disease, inflammatory bowel disease, parasitic infection and bile acid diarrhoea can cause similar symptoms.

Hepatic Encephalopathy

Hepatic encephalopathy is a complication of advanced liver disease. It can cause confusion, altered behaviour, poor concentration, drowsiness and, in severe cases, reduced consciousness.

Certain intestinal bacteria produce substances that contribute to toxin accumulation. Rifaximin can reduce the activity of some of these bacteria and lower the risk of recurrent episodes.

It is commonly used alongside lactulose rather than as a replacement for it. Treatment must be supervised by a liver specialist.

Rifagut 400 should not be used to manage new confusion at home. Sudden confusion in someone with liver disease requires urgent medical assessment.

Small Intestinal Bacterial Overgrowth

Small intestinal bacterial overgrowth, or SIBO, refers to an excessive or altered bacterial population in the small intestine. Possible symptoms include bloating, excessive gas, abdominal discomfort and diarrhoea.

Doctors sometimes prescribe rifaximin for selected cases of SIBO. However, the definition, testing methods and ideal antibiotic regimen remain uncertain.

Treatment should also address possible underlying causes, such as altered intestinal movement, previous surgery or nutritional deficiencies. Repeated self-treatment can delay the correct diagnosis and increase antibiotic-related risks.

Other Uses

A doctor may prescribe rifaximin for another gut-related condition based on individual clinical judgement and local guidance.

An off-label prescription does not necessarily mean that the medicine is unsafe. It means the specific use may not be included in the approved product information. Your doctor should explain why it is being recommended.

Rifagut 400 Dosage And How To Take It

There is no single Rifagut 400 dosage for every condition. The number of tablets, frequency and duration depend on:

The 400 mg printed on the pack is the strength of each tablet. It is not automatically the correct daily dose.

International rifaximin regimens for certain conditions may use 200 mg or 550 mg tablets. Do not convert these schedules into Rifagut 400 tablets or split tablets unless your doctor or pharmacist specifically instructs you to do so.

How To Take Rifagut 400

Follow the instructions on your prescription.

General administration advice includes:

• Take the medicine at the prescribed times.
• Swallow the tablet with water.
• It can generally be taken with or without food.
• Take each dose at approximately the same time every day.
• Do not take more tablets than prescribed.
• Do not stop early simply because you feel better.
• Do not extend or repeat the course without medical advice.

If nausea or stomach discomfort occurs, ask your doctor whether taking the tablet with food may help.

Missed Dose And Overdose

Missed Dose

Take the missed dose when you remember. However, skip it if your next scheduled dose is due soon.

Do not take two doses together to make up for a missed tablet.

Overdose

Taking more than the prescribed dosage may increase your risk of side effects.

Contact a doctor or emergency medical service if you take an excessive amount, particularly if you experience severe nausea, vomiting, dizziness, breathing difficulty or unusual drowsiness.

Rifagut 400 Side Effects

The type and frequency of Rifagut 400 side effects can vary according to the condition being treated, the dosage and your overall health.

Common Side Effects

Possible side effects include:

• Nausea
• Headache
• Dizziness
• Tiredness
• Abdominal pain
• Bloating or excessive gas
• Constipation
• Diarrhoea
• Joint pain
• Muscle discomfort
• Swelling of the hands, feet or ankles
• Skin rash or itching

Nausea, constipation or joint pain may also be related to the underlying digestive or liver condition. Contact your doctor if symptoms persist, become severe or interfere with your daily routine.

Serious Side Effects

Stop taking the medicine and seek urgent medical attention if you develop:

• Swelling of your face, lips, tongue or throat
• Difficulty breathing or swallowing
• A severe or widespread rash
• Blistering or peeling skin
• Fainting
• Severe or persistent diarrhoea
• Bloody stools
• High fever
• Severe abdominal pain
• Rapidly increasing swelling
• Marked weakness or confusion

Almost all antibiotics can occasionally contribute to Clostridioides difficile associated diarrhoea. This can develop during treatment or after the antibiotic course has ended.

Do not use an anti-diarrhoeal medicine to manage severe antibiotic-associated diarrhoea without medical advice.

Does Rifagut 400 Cause Dehydration?

Dehydration is not usually a direct effect of rifaximin. However, continued diarrhoea or vomiting can cause your body to lose water and electrolytes.

Possible signs of dehydration include:

• Dry mouth
• Excessive thirst
• Dark urine
• Passing less urine
• Dizziness
• Weakness
• Rapid heartbeat
• Unusual drowsiness

Drink suitable fluids and oral rehydration solution when advised. Seek medical help if you cannot keep fluids down, have reduced urination or feel faint.

Infants, older adults and people with kidney or heart disease can become dehydrated more quickly.

Precautions And Warnings

Tell your doctor about your health conditions before taking Rifagut 400.

Extra caution may be needed if you:

• Have severe liver disease
• Have kidney disease
• Are pregnant or planning pregnancy
• Are breastfeeding
• Have previously had antibiotic-associated colitis
• Have a known allergy to rifaximin or another rifamycin antibiotic
• Have fever or blood in your stools
• Have persistent or recurrent diarrhoea
• Are taking warfarin, cyclosporine or several other medicines
• Are treating a child or older adult

Rifaximin exposure in the bloodstream may be higher when you have severe liver impairment. Your doctor may need to monitor you more closely.

Pregnancy And Breastfeeding

Human safety information for rifaximin during pregnancy is limited. Animal studies have raised concerns about possible harm to the developing baby.

Tell your doctor if you are pregnant, could be pregnant or are planning a pregnancy. The medicine should be used only when your doctor considers it necessary.

It is not clear whether rifaximin passes into human breast milk. Discuss the possible benefits and risks with your doctor before taking it while breastfeeding.

Rifagut 400 Drug Interactions

Although rifaximin has limited absorption, interactions can still occur.

Cyclosporine

Cyclosporine can substantially increase rifaximin exposure in the bloodstream. Your doctor may need to assess whether the combination is appropriate.

Warfarin

Rifaximin may affect the response to warfarin. Your doctor may monitor your international normalised ratio, or INR, and adjust your warfarin dosage when required.

Other Medicines

Tell your doctor about:

• Prescription medicines
• Over-the-counter medicines
• Herbal products
• Vitamins and supplements
• Other antibiotics
• Medicines for liver disease

Do not stop or change any regular medicine without medical advice.

Who Should Avoid Rifagut 400?

Do not take Rifagut 400 if you have had a serious allergic reaction to:

• Rifaximin
• Rifampicin
• Rifabutin
• Rifapentine
• Another rifamycin medicine
• Any ingredient in the tablet

You should not use it as routine self-treatment for every episode of diarrhoea.

Seek medical assessment before taking an antibiotic if you have fever, bloody stools, severe pain, repeated vomiting, recent hospitalisation or significant dehydration.

Rifagut 400 Versus Systemic Antibiotics

Rifaximin and systemically absorbed antibiotics have different roles.

A gut-selective antibiotic is not necessarily stronger or weaker. It is designed for a different clinical purpose.

Rifagut 400 should not replace an antibiotic needed for an invasive infection or an infection outside the digestive tract.

Diagnostic Tests Before Starting Rifagut 400

Testing is not required before every prescription. Your doctor will choose investigations based on your symptoms and medical history.

Tests For Acute Diarrhoea

Testing may include:

• Stool culture or molecular testing
• Stool examination for parasites
• CBC test
• Kidney function test
• Electrolyte test

Stool testing may be particularly important when you have fever, bloody diarrhoea, severe illness, recent antibiotic use or weakened immunity.

Tests For Chronic Diarrhoea Or IBS-D

Your doctor may consider:

• Coeliac disease antibody tests
• Faecal calprotectin or lactoferrin
• Testing for Giardia
• Thyroid function tests
• Tests for nutritional deficiencies
• Investigations for bile acid diarrhoea
• Colonoscopy when warning signs or screening indications are present

IBS-D is diagnosed from your symptom pattern after appropriate evaluation. There is no single blood test that confirms Irritable Bowel Syndrome.

Tests For SIBO

A hydrogen or methane breath test may sometimes support the diagnosis. However, these tests have limitations and must be interpreted with your symptoms and risk factors.

Tests For Hepatic Encephalopathy

Hepatic encephalopathy is primarily a clinical diagnosis. Your doctor may use blood tests, urine tests, imaging or other investigations to look for triggers such as:

• Infection
• Bleeding
• Constipation
• Kidney dysfunction
• Electrolyte imbalance
• Dehydration
• Sedative medicines

An ammonia level alone should not be used to diagnose, grade or guide the treatment of hepatic encephalopathy.

When Should You Contact A Doctor?

Contact your doctor promptly if:

• Your symptoms do not improve.
• Your diarrhoea becomes worse.
• You develop constipation that is severe or persistent.
• Nausea prevents you from eating or drinking.
• Joint pain becomes significant.
• You develop swelling of your feet or abdomen.
• You notice a new rash.
• Your symptoms return soon after treatment.
• You develop signs of dehydration.

Seek urgent care for bloody stools, high fever, breathing difficulty, severe abdominal pain, fainting, confusion or an allergic reaction.

Key Takeaways

• Rifagut 400 contains 400 mg of rifaximin.
• It is a prescription, gut-selective rifamycin antibiotic.
• Rifagut tablet uses may include selected bacterial diarrhoea, IBS-D, hepatic encephalopathy and some cases of SIBO.
• It is not suitable for every type of diarrhoea.
• Rifagut 400 dosage varies according to the condition and must come from your prescription.
• Possible side effects include nausea, constipation, headache, dizziness, abdominal pain and joint pain.
• Continued diarrhoea or vomiting can contribute to dehydration.
• Severe or bloody diarrhoea requires medical assessment.
• Do not repeat or extend treatment without consulting your doctor.

Digestive symptoms can arise from infection, inflammation, food intolerance, liver disease and several other conditions. Accurate evaluation helps you receive suitable treatment rather than taking an unnecessary antibiotic.

Metropolis Healthcare supports timely health evaluation with more than 4,000 tests, speciality testing, accurate results and reliable reports. Depending on your symptoms, your doctor may recommend blood, stool, liver function or other relevant tests. Metropolis also provides convenient home sample collection through a strong network of 10,000 touchpoints. You can book through the website, app, call or WhatsApp, making preventive testing and ongoing health monitoring more accessible.

FAQs About Rifagut 400

How Long Does Rifagut 400 Take To Work?

The response time depends on the condition. Some people with bacterial diarrhoea may notice improvement within a few days. IBS-D and other conditions may take longer. Contact your doctor if symptoms worsen or do not improve within the expected period.

Can Rifagut 400 Be Taken On An Empty Stomach?

Rifaximin can generally be taken with or without food. Follow your prescription. Taking it with food may help if you experience nausea or stomach discomfort.

Is Rifagut 400 Safe During Pregnancy?

Safety information during pregnancy is limited, and animal studies suggest possible fetal risk. Take it only when your doctor believes the expected benefit outweighs the potential risk.

Can Rifagut 400 Cause Constipation?

Yes, constipation has been reported in some people taking rifaximin. Tell your doctor if it is severe, painful or persistent.

Can Rifagut 400 Cause Joint Pain?

Joint pain can occur, particularly in people receiving rifaximin for liver-related conditions. Seek medical advice if the pain is severe, accompanied by swelling or does not settle.

Does Rifagut 400 Cause Dehydration?

It does not usually cause dehydration directly. However, persistent diarrhoea, nausea or vomiting can lead to fluid loss. Monitor your hydration and seek help if you feel faint or pass very little urine.

Is Rifagut 400 A Strong Antibiotic?

Antibiotics should not be described simply as strong or weak. Rifaximin is a gut-selective antibiotic designed for particular intestinal conditions. It is not appropriate for most systemic or invasive infections.

Can Rifagut 400 Be Taken Long Term?

Long-term rifaximin may be prescribed for selected people with recurrent hepatic encephalopathy. Long-term use should be supervised by a specialist. Do not continue Rifagut 400 beyond the prescribed period on your own.

Can You Drink Alcohol While Taking Rifagut 400?

There is limited information about a direct interaction. However, alcohol may worsen dehydration, digestive symptoms and liver disease. Ask your doctor whether it is safe for your specific condition.

Can Rifagut 400 Treat Every Type Of Diarrhoea?

No. Diarrhoea may be caused by viruses, parasites, invasive bacteria, medicines or non-infectious digestive conditions. Rifagut 400 will not treat every cause.

References

1. DailyMed. Xifaxan, Rifaximin Tablets: Full Prescribing Information. United States National Library of Medicine; updated 2025.
2. Lembo A, Sultan S, Chang L, Heidelbaugh JJ, Smalley W, Verne GN. AGA clinical practice guideline on the pharmacological management of irritable bowel syndrome with diarrhoea. Gastroenterology. 2022;163(1):137-151. PMID: 35738725.
3. Quigley EMM, Murray JA, Pimentel M. AGA clinical practice update on small intestinal bacterial overgrowth: expert review. Gastroenterology. 2020;159(4):1526-1532. PMID: 32679220.
4. Bajaj JS, Jakab SS, Jesudian AB, Rahimi RS, Duarte-Rojo A, Chen PH, et al. ACG clinical guideline: hepatic encephalopathy. Am J Gastroenterol. 2026;121(3):588-618. PMID: 41773757.
5. Smalley W, Falck-Ytter C, Carrasco-Labra A, Wani S, Lytvyn L, Falck-Ytter Y. AGA clinical practice guidelines on the laboratory evaluation of functional diarrhoea and diarrhoea-predominant irritable bowel syndrome in adults. Gastroenterology. 2019;157(3):851-854. PMID: 31302098.