Rifaximin

Rifaximin is a semisynthetic, rifamycin-based non-systemic antibiotic, meaning that the drug will not pass the gastrointestinal wall into the circulation as is common for other types of orally administered antibiotics. It is licensed for use to treat diarrhea caused by E. coli. It is not effective against Campylobacter jejuni, and there is no evidence of efficacy against Shigella or Salmonella species.

It may be efficacious in relieving chronic functional symptoms of bloating and flatulence that are common in irritable bowel syndrome.

In 2005, it received orphan drug status for the treatment of hepatic encephalopathy.

It is currently sold in the U.S. under the brand name Xifaxan by Salix Pharmaceuticals.

It's also sold in Europe under the name Spiraxin and Zaxine, both of which seem to be cheaper solutions. There isn't a generic version of the drug.