Rifaximin

Also known as: Xifaxan (brand), non-absorbed rifamycin antibiotic

Other

In plain English

Rifaximin is an antibiotic that stays mostly in the gut instead of being absorbed into the body, so it treats gut problems with fewer body-wide antibiotic effects. It is used for travelers' diarrhea, IBS with diarrhea, and to prevent a liver-related confusion (hepatic encephalopathy), and off-label for small intestinal bacterial overgrowth (SIBO). Because it isn't absorbed, side effects are usually mild.

The science

Rifaximin is a minimally absorbed (<0.4%) rifamycin derivative that inhibits bacterial DNA-dependent RNA polymerase, acting locally in the gut lumen with broad activity and low systemic exposure. It is FDA-approved for travelers' diarrhea, IBS-D, and hepatic encephalopathy; for SIBO (off-label), a systematic review/meta-analysis found an overall eradication rate near 60% with dose-dependent efficacy (higher daily doses more effective).

References

• Wang J et al., efficacy of rifaximin in SIBO (systematic review/meta-analysis), Expert Rev Gastroenterol Hepatol 2021
• Scarpellini E et al., rifaximin dose-finding study for SIBO, Aliment Pharmacol Ther 2005