Rifaximin (brand name Xifaxan) is a non-systemic, broad-spectrum antibiotic derived from rifamycin. It’s unique because it stays almost entirely within the gut, meaning it kills bacteria locally without significantly entering the bloodstream.
 
Primary Clinical Uses
Small Intestinal Bacterial Overgrowth (SIBO) – reduces excess bacteria that cause bloating, gas, and IBS-like symptoms.
Irritable Bowel Syndrome – Diarrhea-Predominant (IBS-D) – improves stool consistency, abdominal pain, and bloating.
Traveler’s Diarrhea – treats E. coli-related gastrointestinal infections.
Hepatic Encephalopathy – lowers ammonia-producing gut bacteria, reducing risk of recurrence.
Off-label: occasionally used for Crohn’s, ulcerative colitis adjunct therapy, and rosacea (via gut–skin axis).