ATC Code A07AA11, D06AX11
Formula C43H51N3O11
Molar Mass (g·mol−1) 785,88
Physical State solid
CAS Number 80621-81-4
PUB Number 6436173
Drugbank ID DB01220
Solubility moderate in water / poor in ethanol


Rifaximin is a semisynthetic, non-systemic antibiotic based on rifamycin, which means the drug does not pass through the gastrointestinal wall and does not enter the bloodstream, as is common with other types of antibiotics. It is used to treat traveler's diarrhea caused by E. coli, to reduce the risk of recurrence of overt hepatic encephalopathy, and to treat diarrhea-dominant irritable bowel syndrome in adult women and men.



Rifaximin acts by inhibiting RNA synthesis in susceptible bacteria by binding to the beta subunit of the bacterial deoxyribonucleic acid (DNA)-dependent ribonucleic acid (RNA) polymerase enzyme. This binding blocks translocation, halting transcription. As a result, the bacteria can no longer synthesize proteins, preventing them from reproducing.


Rifaximin is not absorbed systemically, so there are no data on pharmacokinetics. The half-life is approximately 6 hours.


Side effects

Rifaximin has few unwanted other effects. These side effects are generally mild and rare. This is mainly because very little of the drug is absorbed from the intestine, which means there are no systemic side effects.

Toxicological data

LD50 (rat, oral): > 2000 mg-kg-1


  • Drugbank
  • PubChem
  • Aktories, Förstermann, Hofmann, Starke: Allgemeine und spezielle Pharmakologie und Toxikologie, Elsvier, 2017

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All information used for the content comes from verified sources (recognised institutions, experts, studies by renowned universities). We attach great importance to the qualification of the authors and the scientific background of the information. Thus, we ensure that our research is based on scientific findings.

Markus Falkenstätter

Markus Falkenstätter

Markus Falkenstätter is a writer on pharmaceutical topics in Medikamio's medical editorial team. He is in the last semester of his pharmacy studies at the University of Vienna and loves scientific work in the field of natural sciences.

Mag. pharm Stefanie Lehenauer

Mag. pharm Stefanie Lehenauer

Stefanie Lehenauer has been a freelance writer for Medikamio since 2020 and studied pharmacy at the University of Vienna. She works as a pharmacist in Vienna and her passion is herbal medicines and their effects.

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