Rifaximin (Rifaximin 200 mg / 550 mg) – Patient Guide (UK)

Rifaximin is an antibiotic medicine used to treat certain intestinal infections and conditions. It works mainly within the gut, with very low absorption into the bloodstream, which can help reduce effects on the rest of the body.

This guide is designed for patients in the United Kingdom and explains what rifaximin is, how it works, how it is used, and practical safety advice. Always follow the instructions provided with your medicine and speak to a healthcare professional if you have questions.

Basic product information

Note: Availability and packaging can vary by manufacturer. If you are unsure which strength you have, check the label.

Mechanism of action: how rifaximin works

Rifaximin belongs to the rifamycin antibiotic family. It works by:

• Blocking bacterial RNA synthesis: It interferes with the function of bacterial RNA polymerase.
• Reducing growth and survival of susceptible gut bacteria: This helps clear infections or reduce bacterial overgrowth associated with certain bowel symptoms.
• Targeting the intestinal environment: Because rifaximin is poorly absorbed into the blood, much of its activity stays in the gastrointestinal tract.

Importantly, rifaximin affects mainly bacteria in the gut. It is therefore often used for conditions involving intestinal bacteria rather than infections that are spread throughout the body.

Pharmacokinetics: what happens to the medicine in the body

Pharmacokinetics describes how a medicine is absorbed, distributed, metabolised, and eliminated.

• Absorption: Rifaximin has very low systemic absorption. Most of the dose remains in the intestines.
• Distribution: Because absorption is low, blood levels are typically minimal.
• Metabolism: Any metabolism in the body is limited; the medicine is largely acting locally.
• Elimination: The medicine is mainly cleared via the gastrointestinal tract. Only small amounts reach systemic circulation and are then cleared.

This “local gut” profile is one reason rifaximin is often chosen when doctors want to limit whole-body exposure to antibiotics.

Typical uses in the UK

Rifaximin is used for specific intestinal conditions. The exact approved indications can depend on the product and the current UK regulatory status. In everyday clinical practice, rifaximin may be used for:

• Travellers’ diarrhoea due to certain bacteria, especially where non-invasive infection is suspected
• Hepatic encephalopathy (broadly: confusion or neurological symptoms due to liver disease), commonly as part of ongoing management
• Other bowel-related bacterial conditions as determined by local clinical guidance and specialist assessment

If you are considering rifaximin, the most important step is to use it for the correct condition. Taking an antibiotic for the wrong problem can be ineffective and can increase the risk of side effects or antibiotic resistance.

When to take rifaximin: timing and routine

Follow the schedule provided with your medicine. In many regimens:

• You may be instructed to take two or three doses per day depending on the strength and condition.
• Try to take doses at regular times to keep antibiotic activity steady in the gut.
• Complete the full course unless a clinician advises otherwise, even if you feel better.

Missed dose: If you miss a dose, take it when you remember unless it is close to the next dose. Do not take a double dose.

Food interactions: can you take rifaximin with meals?

Because rifaximin acts primarily in the gastrointestinal tract, food effects may vary slightly between individuals. In general:

• It can usually be taken with or without food, but follow your local instructions.
• If your stomach is sensitive, taking it with a light meal or snack may improve comfort.

If your product leaflet gives specific instructions, those instructions should be followed.

Alcohol interactions

Rifaximin does not typically have a well-known direct “disulfiram-like” reaction with alcohol. However, drinking alcohol during treatment may:

• Worsen diarrhoea or stomach upset in some people
• Increase nausea or fatigue
• Be particularly important to avoid or limit if you have liver disease (relevant for conditions such as hepatic encephalopathy)

Practical advice: For best tolerance, consider avoiding alcohol until you have finished the course and you feel well again. If you have liver problems, discuss alcohol use with your clinician.

Medicine interactions: what to consider

Even though systemic absorption is low, it is still important to tell a healthcare professional about all medicines and supplements you take. Potential interaction considerations include:

• Other antibiotics: Using multiple antibiotics together may not be appropriate unless advised.
• Medicines that strongly affect gut motility: Severe ongoing diarrhoea can reduce absorption of other medicines and may change how you feel during treatment.
• Immunosuppressants or complex regimens: If you take multiple long-term medicines (especially for liver disease), confirm compatibility.
• Over-the-counter remedies: Anti-diarrhoeal medicines (such as loperamide) may be used in some diarrhoea scenarios but not in others—seek advice, especially if you have fever or blood in your stool.

Tell your pharmacist or clinician if you are taking:

• Warfarin or other anticoagulants
• Medicines for liver disease
• Anti-epileptics
• Strong enzyme-inducing drugs or complex HIV/antiretroviral medicines

Interaction specifics can depend on the exact product and dose. Your pharmacist can check your medicine list quickly and accurately.

Indications: common situations where rifaximin may be considered

In clinical practice, rifaximin may be used when the goal is to reduce certain intestinal bacteria or manage gut-related complications. Common reasons include:

• Travellers’ diarrhoea: Often in adults with suspected bacterial causes, where local antibiotic strategies recommend targeted treatment.
• Hepatic encephalopathy: Used to help reduce gut bacteria that produce substances contributing to encephalopathy in some people with liver disease.
• Recurrent bowel symptoms due to bacterial imbalance: In selected cases, specialists may use rifaximin based on evidence and local protocols.

Important: Not all diarrhoea is bacterial. If you have viral diarrhoea, severe inflammatory bowel conditions, or non-infectious causes, an antibiotic may not help.

Dosing: how rifaximin is commonly prescribed

Dose depends on the condition, your age, kidney/liver status, and the specific strength of your tablets.

• Travellers’ diarrhoea: Dosing regimens in adults are commonly short (often around 3 days), but follow your prescribed schedule.
• Hepatic encephalopathy: Regimens may be longer and sometimes repeated as part of maintenance management.

Because strengths and instructions vary, it is best to follow the dosing on your label or the instructions provided by your healthcare professional. If you are unsure, ask your pharmacist.

General safe-use reminder:

• Do not change the dose to “stop sooner” even if symptoms improve.
• Do not take extra tablets to “make it work faster.”

Safety profile: side effects and when to seek help

Most people tolerate rifaximin well, but like all medicines it can cause side effects. Common and important possible effects include:

Common side effects

• Stomach or gut symptoms: mild abdominal discomfort, nausea, or bloating
• Headache
• Mild diarrhoea (sometimes occurs during antibiotic treatment)

Less common but serious concerns

• Allergic reactions (rare): rash, itching, swelling of the face/lips, breathing difficulties
• Severe or persistent diarrhoea (including watery diarrhoea that doesn’t settle): could indicate a more serious gut infection

Seek urgent medical advice if

• You develop swelling of the face or throat, wheezing, or difficulty breathing
• You have severe diarrhoea, especially with fever, blood, or significant dehydration
• You feel very unwell, faint, or confused (especially if you have liver disease)

Call your pharmacist or clinician promptly if side effects are troublesome or not improving after a short time.

Practical use tips for patients

• Hydration: If you’re taking rifaximin for diarrhoea, drink fluids regularly. Consider oral rehydration solution if needed.
• Complete the course: Even if symptoms improve quickly, completing the recommended duration helps reduce relapse.
• Don’t share antibiotics: Your medicine may not be appropriate for someone else’s symptoms.
• Store correctly: Keep tablets in their original packaging and follow label storage instructions (usually at room temperature away from moisture).
• Track symptoms: Note stool frequency, fever, blood in stool, and how you feel. This helps clinicians assess whether treatment is working.

Alternative options (depending on the condition)

Alternatives depend strongly on why rifaximin is being used. Your clinician may consider other treatments such as:

For infectious diarrhoea (travellers’ diarrhoea)

• Other oral antibiotics (choice depends on resistance patterns and severity)
• Supportive care only for mild cases (fluids and electrolytes)
• Anti-diarrhoeal medicines in specific circumstances (not suitable for everyone)

For hepatic encephalopathy

• Lactulose and other bowel-regulating strategies are often used
• Specialist-led combinations of gut-targeted therapies

Important: Do not switch medications without medical advice. The best option depends on your diagnosis, severity, and medical history.

Market and legal context in the United Kingdom

In the UK, medicines are regulated to ensure safety, quality, and appropriate use. Patient supply and use depend on the medication’s classification and licensing status.

• Regulation: Medicines in the UK are authorised by the appropriate authorities and must meet standards for manufacture and quality.
• Antibiotic stewardship: The UK places strong emphasis on using antibiotics appropriately to help limit antibiotic resistance.
• Guidance: Healthcare professionals typically follow national and local guidance for the treatment of diarrhoea, gut infections, and liver-related complications.
• Safety monitoring: Side effects are monitored via established reporting systems.

For the most accurate and up-to-date status of rifaximin products (including indications and availability), your pharmacist can advise based on the exact product and strength.

Recent guidance and stewardship approach (UK context)

While individual recommendations vary by clinical scenario, recent UK-focused practice continues to emphasise:

• Targeting antibiotics to likely bacterial causes
• Short, appropriate duration when antibiotics are needed
• Reviewing symptoms if there is no improvement after the expected timeframe
• Extra caution in severe diarrhoea or diarrhoea with blood/fever
• Specialist involvement where hepatic encephalopathy or complex liver disease is involved

If your symptoms do not improve as expected, seek advice rather than extending treatment yourself.

Delivery and availability (online pharmacy in the UK)

Online pharmacy availability depends on your location, stock levels, and the product strength/manufacturer you order. When ordering rifaximin through an online service:

• Check product strength: Ensure you select the correct tablet strength (commonly 200 mg or 550 mg depending on the product).
• Delivery estimates: Dispatch time and delivery day depend on courier schedules and your postcode area.
• Packaging: Medicines are typically supplied in tamper-evident packaging with patient information.
• Temperature and storage: Most rifaximin tablets do not require refrigeration, but follow the label instructions.

Availability note: If a specific brand is unavailable, the pharmacy may offer an equivalent alternative where appropriate and permitted. Confirm the appearance and strength with your supplier.

FAQ: common questions about rifaximin

1) What is rifaximin used for?

Rifaximin is an antibiotic used for specific intestinal conditions. In the UK, it may be used for situations such as certain cases of travellers’ diarrhoea and for hepatic encephalopathy in people with liver disease, depending on the approved indication and clinical judgement.

2) How long does rifaximin take to work?

Many people notice improvement within the first 24–72 hours, but this depends on the condition being treated and the cause of symptoms. If you’re not improving after the expected timeframe, contact your pharmacist or clinician.

3) Can I take rifaximin with food?

It is commonly taken with or without food. If your patient leaflet advises a specific method, follow that advice. Taking with a light meal may help if you experience mild stomach upset.

4) Can I drink alcohol while taking rifaximin?

There is no widely recognised direct interaction like some other antibiotics, but alcohol may worsen dehydration, nausea, or diarrhoea. If you have liver disease, it is especially important to be cautious. When in doubt, avoid alcohol and ask your healthcare professional.

5) What should I do if my diarrhoea gets worse?

Stop and seek medical advice if you develop severe diarrhoea, blood in stool, fever, signs of dehydration, or you feel very unwell. Persistent or worsening diarrhoea can indicate a more serious gut condition that needs assessment.

6) Is rifaximin safe for everyone?

Most people tolerate rifaximin well, but safety depends on your medical history and other medicines. You should discuss use with a healthcare professional if you have liver disease, allergies to rifamycin antibiotics, or significant ongoing bowel conditions.

7) Are there alternatives to rifaximin?

Yes, alternatives depend on the diagnosis. For diarrhoea, supportive care and other antibiotics may be considered based on severity and likely cause. For hepatic encephalopathy, other gut-targeted treatments (such as lactulose) may be used. Your clinician can guide you.

8) Can I use rifaximin for viral diarrhoea?

Antibiotics like rifaximin generally do not help viral infections. If you are unsure what is causing your symptoms, consider getting medical advice—especially if symptoms are severe, last more than a few days, or include blood or fever.

9) What happens if I miss a dose?

Take it as soon as you remember unless it is close to the next scheduled dose. Do not take a double dose.

10) Where can I report side effects?

If you experience side effects, speak to your pharmacist or clinician. You can also report concerns through the UK medicines safety reporting system (details are provided by NHS and medicines safety channels).

Summary

Rifaximin is an antibiotic designed to act largely within the gut. It is used for specific intestinal conditions and may be an option in situations such as certain diarrhoea episodes and hepatic encephalopathy, depending on clinical assessment and UK guidance. To use rifaximin safely, take it as directed, complete the full course, stay hydrated if you have diarrhoea, and seek medical help if you develop severe symptoms or signs of allergy.

Need help? If you want, tell us what rifaximin strength you have and what condition it’s intended for, and we can help you understand how to take it safely and what to watch for.