Rifaximin Products | Cleanchem - Rifaximin is an antibiotic used primarily to treat gastrointestinal disorders like irritable bowel syndrome with diarrhea (IBS-D) and traveler's diarrhea. It works by inhibiting bacterial RNA synthesis, particularly targeting bacteria in the intestines. Rifaximin is non-absorbable, meaning it stays in the gut and does not significantly enter the bloodstream.