Rifaximin 550mg tablets are a gut-selective rifamycin antibiotic used primarily for reducing the risk of overt hepatic encephalopathy recurrence and for managing irritable bowel syndrome with diarrhea (IBS-D) in adults, with additional use in traveler’s diarrhea varying by market authorization. The drug remains minimally absorbed, acting locally in the intestinal lumen to inhibit bacterial RNA synthesis and modulate gut microbiota and ammonia-producing bacteria relevant to encephalopathy. Availability of 550mg formulations is widespread globally under various brands, with usage guided by local labeling and clinical guidelines; it is not intended for systemic infections and is selected based on confirmed indications.