Rifaximin (Xifaxan)

Rifaximin (Xifaxan)

Rifaximin is an antibiotic that works within a specific targeted area, the intestine. It helps to kill bacteria in the intestine known as Escherichia coli, which can often be the cause of a condition called traveler’s diarrhea. More information

A doctor will review your order and write you a prescription, if appropriate. This prescription is then forwarded to a pharmacy. The pharmacy will have your medicine delivered to you within one to three working days. Read more about this process here.

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Rifaximin is a form of antibiotic, designed to kill the bacteria that causes illness and pain. The active ingredient in this substance, Rifaximin acts within the intestine and usually isn’t absorbed into the bloodstream, reducing the risk of side effects.  

What is Rifaximin? 

Rifaximin is an antibiotic that works within a specific targeted area, the intestine. It helps to kill bacteria in the intestine known as Escherichia coli, which can often be the cause of a condition called traveler’s diarrhea. Travelers diarrhea happens when an individual is exposed to substances or foods that their stomach and digestive system isn’t used to. When you eat new food or drink water from a country that you’re not used to, you’re more likely to have uncomfortable bowel movements.  

This medication is only available when given by prescription, and it should not be taken by people who have other issues aside from diarrhea, such as severe stomach pains, bloody stool movements, or a persistent fever. Rifaximin works by reducing the growth of bacteria, causing it to die out. This medicine is only available in tablet form.  

Some forms of Ecoli can be deadly and therefore it is important that you get a checkup with your doctor as soon as possible, to check your blood pressure and levels of hydration. 

When is Rifaximin used? 

Rifaximin is most commonly given for the treatment of traveler's diarrhea. However, Rifaximin can be effective at preventing and treating other forms of illness too. In some cases, Rifaximin is used to prevent the onset of a condition called hepatic encephalopathy. People suffering from hepatic encephalopathy have poorly functioning livers. The condition can cause the brain to work poorly, and Rifaximin may help you to think more clearly. 

Rifaximin works by killing bacteria specifically within the intestine and preventing further growth. Crucially, this medicine will only treat bacterial infections and will not treat any form of viral infection such as the flu. Using any kind of antibiotic for reasons beyond it’s intended use could cause future problems, such as resistance.  

How do you use Rifaximin? 

When using any new medication, it’s always important to read through the instructions provided in your patient leaflet. The information leaflet included with your medication will provide you with useful information on how to take the tablet, and which other medications you should avoid when you’re using this substance.  

Follow the instructions given to you during your consultation carefully, and make sure that you do not take more or less of the medication than was prescribed to you. If you have any questions, contact your consultant or a local pharmacist. The way that you manage your treatment will depend on a number of factors, including what you are using Rifaximin for.  

To take this antibiotic effectively, you will need to swallow the pill whole with a glass of water. Do not crush the pill. For the best outcomes, try to take the pill at the same times throughout the day. To help you remember, you may want to set an alarm, and take your medication at a specific time each day.   

What dosages are there? 

The dosage for Rifaximin will depend on your medical condition, as well as how you might have responded for similar antibiotic treatments in the past. If you are using Rifaximin for traveler’s diarrhea, then your doctor will usually recommend taking one tablet three times per day. You will be able to take Rifaximin either with or without food.  

You should not use Rifaximin for travelers’ diarrhea for more than 3 days.  

If you have been given Rifaximin for hepatic encephalopathy, you will need to take it by mouth twice per day. Just take one tablet with each dose, and make sure that you use the medication at evenly spaced times. You will be told how long you should continue to take this medication, and you should continue to use the pills for as long as recommend. Do not stop taking the pills before you have run out of the prescribed amount, even if your symptoms seem to have disappeared.  

If you miss a pill of Rifaximin, take it as soon as you remember, but do not double up on pills to make up for the one that you have missed. Tell your doctor if you’re still having issues with diarrhea after 2 days of using this medication, as you may need a different treatment. Tell your doctor immediately if you have a fever alongside your diarrhea when using Rifaximin.  

What are the side effects of Rifaximin? 

Rifaximin is a unique form of antibiotic because it is designed to work on a very specific area of the body. Because this medication works actively within the intestines, it’s not usually absorbed into the blood stream. The less of a medication that you get into your blood stream, the lower your chances of side effects become.  

However, just because the risk of side effects with this substance are low, doesn’t mean that some people won’t react poorly to Rifaximin. In some cases, you may find that you have some common side effects when you first begin using the medication, as your body won’t be used to the new substances yet. These common side effects might include gastrointestinal symptoms like feelings of sickness or a general stomachache. Some people also suffer from drowsiness, fatigue, and headaches.  

In some rare conditions, this medication may cause a severe issue with the intestines that’s known as clostridium difficile diarrhea. This condition occurs when you have a specific kind of resistant bacteria in your system. The problem may happen either during your treatment, or months after you have stopped using the medication. Tell your doctor if you ever develop: 

  • Blood or mucus in your stool; 
  • Persistent diarrhea; 
  • Pain and cramping in your stomach. 

Avoid using opioid or anti-diarrhea medications if you have any of the side effects above, as they can make your condition worse.  

While it’s rare to have a severe allergic reaction to this medication, you should always be aware of the symptoms of a reaction. Seek medical attention immediately if you notice a rash or itching anywhere on your body, discomfort caused by swelling in the throat, tongue or face, or severe dizziness. Seek help straight away if after taking Rifaximin you have trouble breathing.  

When shouldn't you use Rifaximin? 

Some people will be more likely to have side effects when taking Rifaximin because of their medical background or condition. It is important to answer all of the questions asked by your consultant and fill out your forms truthfully to ensure that you are getting a safe treatment for your needs. Tell your consultant about your medical history, particularly if you have ever been allergic to any drugs similar to Rifaximin, or if you have other allergies that the consultant needs to be aware of.  

Rifaximin can include inactive ingredients that might lead to allergic reactions and other issues. Before you use this medication, keep in mind that Rifaximin can cause live vaccines using bacteria not to work as they should. It is important not to have any vaccinations or immunizations when you are using this medication unless your doctor advises otherwise. You should also inform your doctor or dentist about any medications that you are using, including Rifaximin, before you have any procedure. 

Do not use Rifaximin if you have other symptoms aside from diarrhea, such as blood or mucus in your stool, or you have a significant fever. Make sure that you are getting the right treatment for your condition.  

During pregnancy and nursing, this medication should only ever be used when it is clearly necessary. Make sure that you discuss the benefits and risks with your doctor in depth before using Rifaximin.  

Does Rifaximin interact with any other medications? 

In some cases, when you take two medications at the same time, they can interact poorly with each other. When drug interactions occur, one or more of the medications that you are using might stop working as they’re supposed to. In some cases, drug interactions can also increase your chances of dangerous or severe side effects.  

While there are not many interactions currently listed for Rifaximin, it is important to tell your consultant about all of the medications that you are taking just in case. This will include any substances that you have been prescribed by a doctor, as well as over the counter and herbal medications. Keep a list of all the non-prescription and prescription drugs that you take to help you. Do not change the dosage of any medicine you are using without approval.  

Although it is unlikely that most antibiotics will affect the hormonal birth control medications that women take like the patch or pills, some antibiotics may decrease their effectiveness. If you are using hormonal birth control at the same time as Rifaximin, you might want to ask your consultant whether it’s safe to use this pill without an additional form of contraception.  

Where can you buy Rifaximin? 

You can only buy this product by your pharmacy.   

Can you get Rifaximin without a prescription?  

Antibiotics such as Rifaximin are not available to use without a prescription.


BNF Nice, online, 2019  “Rifaximin” [Accessed 20th of November 2019] Available on: https://bnf.nice.org.uk/drug/rifaximin.html 

Drugs.com, online, 2019 “Rifaximin”  [Accessed 20th of November 2019] Available on: https://www.drugs.com/mtm/rifaximin.html 

Medicine.net, online, 2019 “Rifamixin” [Accessed 20th of November 2019] Available on:  https://www.medicinenet.com/rifaximin/article.htm 

Medline plus, online, 2019, "Rifaximin", [Accessed 20th of November 2019] Available on: https://medlineplus.gov/druginfo/meds/a604027.html 

Assessed by:

Dr Imran Malik, General practitioner
Registration number: GMC: 4741365

Dr Imran Malik studied undergraduate medicine at King's College University in Central London and clinical studies at the prestigious King's College Hospital. He graduated with a MBBS degree in 2000 and went on to gain postgraduate memberships with the Royal Society of Medicine and also General Practice in 2006.