Rifaximin (Rifaximin 550 mg and other strengths) – Patient Information

Rifaximin is an antibiotic medicine used for specific gut conditions. It works locally in the intestines, with very limited absorption into the bloodstream. This can help target certain infections while reducing the likelihood of widespread effects elsewhere in the body.

This guide is designed to be patient-friendly and UK-focused, covering how rifaximin works, when it is used, what to expect, how to take it, and important safety considerations.

Basic product information

• Active ingredient: Rifaximin
• Common strengths: 200 mg, 400 mg, 550 mg (strengths may vary by product)
• Medicine type: Antibiotic (rifamycin class)
• How it is taken: Usually by mouth (tablets/capsules, depending on brand)
• Where it acts: Primarily in the gastrointestinal tract

Brand names can vary. Your pharmacist can confirm the exact product and strength you have selected.

How rifaximin works (mechanism of action)

Rifaximin belongs to the rifamycin antibiotics. It works by inhibiting bacterial DNA-dependent RNA polymerase. In simple terms, it interferes with how certain bacteria make the essential molecules they need to grow and multiply.

Because rifaximin is designed to act in the gut and has low systemic absorption, its effects are concentrated where many intestinal conditions occur.

Pharmacokinetics (what the body does to the medicine)

Understanding pharmacokinetics can help explain why rifaximin often has fewer whole-body effects than some other antibiotics.

• Absorption: Rifaximin is poorly absorbed from the gastrointestinal tract into the bloodstream.
• Distribution: With low absorption, blood levels are typically low.
• Metabolism: Significant systemic metabolism is limited due to low absorption.
• Excretion: The medicine is largely eliminated via the intestinal route.

In practice, this means side effects may be more related to the gut (for example, nausea or abdominal discomfort) than to effects throughout the body.

Typical uses in the UK

Rifaximin is used for certain diagnosed gastrointestinal conditions and liver-related complications. The exact indications depend on your local prescribing information and the licensed product in the UK.

Common clinical indications include:

• Hepatic encephalopathy: to help reduce episodes in adults with liver impairment (particularly in prevention of recurrence).
• Travellers’ diarrhoea: in some settings, for adults when caused by susceptible bacteria (use depends on local guidance and availability of alternatives).
• Small intestinal bacterial overgrowth (SIBO): in selected cases, often based on specialist assessment and local practice.
• Diarrhoea related to specific bacterial causes: depending on diagnosis and susceptibility patterns.

Your pharmacist can help confirm whether your product is intended for the condition you are treating and whether it matches the dosing schedule provided.

Timing: when to take rifaximin and how long for

Dosing schedules can differ between conditions and product strengths. Always follow the schedule provided with your medication or by your healthcare professional.

General timing tips:

• Consistency matters: Take doses at evenly spaced times to maintain effective levels in the gut.
• Do not double up: If you miss a dose, take it when you remember unless it’s close to your next dose—then skip the missed dose.
• Complete the course (when advised): Completing a prescribed course helps reduce the chance of recurrence or treatment failure.

If you are unsure about the timing for your specific strength, check the label or ask your pharmacist.

Food interactions and taking with meals

Rifaximin’s absorption is low and its action is largely local, so food interactions are generally less pronounced than for some other antibiotics. However, taking it with or without food can affect tolerance and how you feel.

Practical approach:

• Follow the instructions on your medicine label.
• If your stomach feels unsettled, you may find it easier to take rifaximin with food (unless your product information advises otherwise).
• Avoid skipping meals if it helps reduce nausea or cramps.

If you have been told to take it at a particular time (for example, in relation to meals), adhere to that schedule.

Alcohol interactions

There is no universally applicable “never drink alcohol” rule for rifaximin in the way there is with some other antibiotics. However, alcohol can worsen many underlying conditions—especially liver-related problems—making it an important consideration.

Key points for alcohol use:

• If you have liver disease: it is strongly recommended to limit or avoid alcohol, as it can increase strain on the liver and worsen symptoms.
• If you are treating diarrhoea: alcohol may worsen dehydration and stomach upset.
• Stop and seek advice if you feel unwell: severe dizziness, unusual rash, or worsening symptoms should be discussed urgently.

Rifaximin interactions with other medicines

Because rifaximin has low systemic absorption, it typically has fewer drug–drug interactions than antibiotics that circulate widely in the body. Even so, medicine interactions can still occur depending on other therapies and your health status.

Always tell your pharmacist if you take:

• Other antibiotics or antimicrobial medicines
• Medicines affecting liver function
• Medicines that you take for long-term conditions (for example, diabetes, heart disease)
• Herbal products (for example, St John’s wort)

Serious interaction warning:

• If you are taking medicines that strongly induce or inhibit certain transporters/enzymes, interaction potential may differ by product information. Your pharmacist can review your current list and check suitability.

If you would like, you can provide a list of your medicines to your pharmacist to check for potential interactions before you start.

Indications (when rifaximin is used)

In the UK, rifaximin is used for specific licensed indications and in line with guidance from healthcare providers and local formularies. Common areas include:

• Reduction of recurrent hepatic encephalopathy episodes: supporting management in adults with liver dysfunction.
• Travellers’ diarrhoea: for suitable patients and circumstances.
• Selected gastrointestinal bacterial overgrowth problems: typically assessed by specialist clinicians where appropriate.

If your condition is not listed above, your pharmacist can help clarify whether rifaximin is the intended treatment and what alternatives are available.

Dosing guidance (general information)

Dosing varies by the condition, your age, your overall health, and the exact product strength. The information below is general and should not replace the dosing schedule given to you for your medicine.

What you should do:

• Check the strength on your pack (mg per tablet/capsule).
• Confirm the frequency (for example, twice or three times daily) and whether it is with or without food.
• Use a pill organiser or phone reminders to support correct timing.

Safety profile and side effects

Like all medicines, rifaximin can cause side effects. Not everyone will get them. Most side effects are mild and related to the gastrointestinal tract.

Common side effects

• Nausea
• Abdominal discomfort or cramps
• Bloating
• Gas
• Vomiting
• Loose stools or changes in bowel habits

Less common but important side effects

• Headache
• Dizziness
• Rash or itching

Seek urgent medical advice if you experience

• Signs of severe allergy: swelling of face/lips, breathing difficulty, severe rash, wheezing
• Severe or persistent diarrhoea: especially with fever, blood in stool, or severe abdominal pain (could indicate a more serious bowel condition)
• Worsening liver-related symptoms: yellowing of the skin/eyes, dark urine, marked fatigue

Special considerations

• Liver disease: Rifamycins can be used in certain liver-related conditions; however, liver status should be monitored as advised.
• Kidney disease: Because systemic absorption is limited, dose adjustment is often less significant, but your pharmacist can check based on the product information and your health history.
• Pregnancy and breastfeeding: Use may depend on the risk/benefit assessment for your individual situation. Discuss with a healthcare professional.

Practical use tips (how to get the best results)

• Take it on schedule: Set reminders, particularly if you need to take it more than once a day.
• Hydration during diarrhoea: If you are taking rifaximin for diarrhoea, focus on fluids. Oral rehydration solutions can be helpful.
• Keep track of symptoms: Note improvement, stool frequency, and any side effects.
• Avoid stopping early: If you feel better quickly, finishing the intended course can be important unless advised otherwise.
• Don’t share with others: Antibiotic use should be tailored to the specific condition and patient.
• Consider gut comfort measures: Gentle foods (such as toast, rice, bananas, soups) can be easier during stomach upset.

When rifaximin may not be suitable

Rifaximin may not be appropriate if you:

• Have a known allergy to rifaximin or other rifamycins
• Have a condition requiring a different antibiotic or urgent evaluation
• Are experiencing severe diarrhoea with red-flag symptoms (such as blood in stool or high fever), which needs prompt medical assessment

If you are unsure, ask your pharmacist to help you decide whether rifaximin is suitable for your situation.

Alternative options

“The best alternative” depends on the condition being treated, the likely cause, and local guidance. Alternatives may include:

• Other antibiotics: selected based on the suspected bacteria and local resistance patterns
• Supportive care: for diarrhoea, oral rehydration and symptom control may be the priority
• Non-antibiotic strategies: for some chronic gut conditions, lifestyle changes and specialist-led therapies may be used

Your pharmacist can explain common alternatives and how their benefits and side effects compare, based on your diagnosis.

Market and legal context in the United Kingdom

In the UK, rifaximin products are supplied in line with medicine regulations and professional healthcare practice. Availability and specific indications depend on:

• UK product licensing and SmPC/PL information
• National and specialist guidance
• Local antimicrobial stewardship strategies
• Whether a product is marketed as an “on prescription” medicine, and associated supply pathways

For the safest and most effective use, rifaximin should be used when it is clinically appropriate for the diagnosed condition and organism likelihood.

UK pharmacies also support antimicrobial stewardship, encouraging appropriate antibiotic selection, correct duration, and avoidance of unnecessary courses.

Recent guidance and stewardship notes

Antibiotic prescribing practices continue to evolve alongside resistance patterns and evidence updates. In the UK, clinicians and pharmacists follow guidance emphasising:

• Targeted use: antibiotics should be used for likely bacterial causes when benefits outweigh risks
• Correct duration: avoid under- or over-treatment
• Review if not improving: if symptoms do not improve after the expected timeframe, reassessment is recommended
• Monitoring for complications: particularly in persistent diarrhoea or in patients with significant comorbidities

If you’re using rifaximin as part of an ongoing management plan, keep your healthcare team informed of improvements or side effects.

Delivery and availability (UK online pharmacy)

Availability can vary by strength and brand. When ordering online, delivery options typically depend on your location within the UK and current stock levels.

• Stock status: Some strengths may be held in limited quantities.
• Dispatch times: Orders are usually dispatched within working days after verification of eligibility and payment.
• Delivery method: Royal Mail or a courier service may be used depending on parcel size and local service.
• Temperature: Store the medicine according to the pack instructions (often at room temperature away from moisture and direct heat).

If you need your medicine urgently, check the website’s delivery estimates or contact customer support before placing the order.

Storing rifaximin

• Keep in the original packaging to protect from light and moisture.
• Store at room temperature unless your pack states otherwise.
• Keep out of the sight and reach of children.
• Do not use after the expiry date printed on the pack.

FAQ about rifaximin

1) What is rifaximin used for?

Rifaximin is used for specific gastrointestinal conditions, including (in appropriate patients) hepatic encephalopathy to help reduce recurrence. It may also be used in some cases of travellers’ diarrhoea and other selected gut conditions, depending on diagnosis and local guidance.

2) How quickly should I feel better?

Many people notice improvement within 24–72 hours for acute gut infections, but this can vary. If you are not improving after the expected timeframe, or symptoms worsen, contact a healthcare professional.

3) Can I take rifaximin with food?

In many cases it can be taken with food to help tolerance, but follow the instructions provided with your specific product. Your label will indicate whether food is allowed or advised.

4) What if I miss a dose?

Take it when you remember unless it is close to the next dose. Do not take a double dose to make up for a missed one.

5) Are there any alcohol restrictions?

There isn’t a universal “complete alcohol ban” with rifaximin for all users, but alcohol can worsen diarrhoea and is particularly risky if you have liver disease. If you have liver impairment, avoiding alcohol is strongly recommended.

6) Does rifaximin cause diarrhoea?

It can sometimes alter bowel habits, and occasionally cause gastrointestinal side effects. However, severe or persistent diarrhoea—especially with blood, fever, or significant pain—should be assessed urgently.

7) What medicines should I check for interactions?

Always tell your pharmacist about your full medicine list, including herbal products. Rifaximin generally has fewer interactions due to low absorption, but checking is still important—especially with medicines affecting liver function or gut microbiome treatments.

8) Is rifaximin the same as other antibiotics?

Rifaximin is a rifamycin antibiotic and is different from many commonly used antibiotics. Its action is largely local in the gut, which can influence suitability for different conditions.

9) Can I use rifaximin for every type of diarrhoea?

Not all diarrhoea is bacterial, and the cause matters. Using antibiotics unnecessarily can be unhelpful and may increase the risk of complications. If symptoms are severe, persistent, or accompanied by warning signs, seek medical advice promptly.

10) What are the warning signs that mean I should seek urgent care?

Seek urgent help if you experience signs of severe allergy (swelling, breathing difficulty, widespread rash), severe worsening abdominal pain, or severe/persistent diarrhoea with blood or high fever.

Summary

Rifaximin is a gut-targeted antibiotic that works by inhibiting bacterial RNA production. Because it is poorly absorbed, it primarily acts within the gastrointestinal tract. It is used in specific conditions—such as hepatic encephalopathy (to help prevent recurrence) and certain diarrhoea-related scenarios—when it is clinically appropriate.

If you have any questions about how to take rifaximin, possible side effects, or whether it is suitable alongside your current medicines, speak to your pharmacist for personalised guidance.