Medicines & Supplements A to Z > Rifaximin


Last updated on 02/07/2021.

Overview   |   Dosage   |    Side Effects   |   Precautions  |   Tips  |   Where To Buy  




DRUG CLASS: Antibiotics

SUB CLASS: Antimycobacterials

USED FOR: Traveller’s diarrhoea, hepatic encephalopathy, irritable bowel syndrome with diarrhoea

– 200 mg, 550 mg (tablets)

What is Rifaximin for?

Rifaximin belongs to a class of medications called antimycobacterial antibiotics. It works by inhibiting the growth of bacteria and is used to treat traveller’s diarrhoea and irritable bowel syndrome with diarrhoea caused by certain bacteria. It is also used to prevent episodes of hepatic encephalopathy, which is a condition of build-up of toxins in the brain in people who have liver disease. It does not work for virus or fungus infections. Rifaximin is poorly absorbed from the gastrointestinal tract, therefore it is not used for systemic infections.

How to use it?

Rifaximin is available as tablets which are taken by mouth. It may be taken with or without food.

Traveller’s diarrhoea that is not associated with fever or bloody stool
200 mg every 8 hours for 3 days.

Prevention of hepatic encephalopathy
550 mg twice daily.

Irritable bowel syndrome with diarrhoea
550 mg every 8 hours for 14 days. Retreat up to 2 times if symptoms recur.

What are the side effects of Rifaximin?

Common side effects of Rifaximin include headache, fatigue, ascites, oedema, muscle spasms, itchiness, gastrointestinal discomforts, flatulence, nausea and vomiting.

Who should not take Rifaximin?

– People allergic to Rifaximin or any component of the formulation.
– People who are experiencing diarrhoea with fever and/or blood in stool.

Pharmacist Tips:

– Report to your doctor immediately if you experience bloody diarrhoea when you use this medication.
– This medication can make you dizzy. Avoid driving or operating machinery until you know how you respond to Rifaximin.
– Drink plenty of water to replace any lost fluids due to diarrhoea.

Common dosing schedule:
For Traveller’s diarrhoea and irritable bowel syndrome with diarrhoea, take Rifaximin every 8 hours.
For prevention of hepatic encephalopathy, take Rifaximin every 12 hours.
Rifaximin can be taken with or without food.

This schedule is for reference only, adjustments may be made according to individual needs.

Some common medications Rifaximin may interact with:

Please notify your doctor or pharmacist if you are taking the above medication, dosage adjustments might be needed.

Where to buy Rifaximin in Hong Kong?

In Hong Kong, Rifaximin is a prescription only medicine, and requires a prescription from a doctor to be purchased in a pharmacy. It can also be obtained from doctors. To find a pharmacy near you, refer to the list of pharmacies (“Authorized Sellers of Poisons”) from the Hong Kong Department of Health. 

For more information about drug names and ingredients, you can visit Hong Kong’s Drug Office at

Need more information?

For detailed information about the use of Rifaximin in children, pregnancy and breastfeeding, and for questions about drug interactions, please check with your pharmacist or doctor.

Disclaimer: our goal is to provide you with the most relevant drug information and common dosage for Hong Kong. This information does not constitute medical advice. For specific treatment recommendations and advice, always discuss with your doctor or pharmacist, and follow the instructions included with your specific medicine.