Rifaximin is a semisynthetic, rifamycin-based non-systemic antibiotic, meaning that very little of the drug will pass the gastrointestinal wall into the circulation as is common for other types of orally administered antibiotics. It is used in the treatment of traveler's diarrhea and hepatic encephalopathy, for which it received orphan drug status from the U.S. Food and Drug Administration in 1998.(wikipedia en)