Rifaximin Pharmacology

Rifaximin, branded as Xifaxan, serves as a specialized rifamycin antibiotic primarily utilized for gastrointestinal conditions rather than systemic infections. Its clinical utility centers on managing hepatic encephalopathy as a second-line agent to lactulose and treating *C. difficile* infections, alongside off-label uses like small intestine bacterial overgrowth and traveler's diarrhea. The drug’s defining characteristic is its negligible oral absorption; approximately 96% is excreted unchanged in feces, ensuring high concentrations remain within the gut while minimizing systemic adverse effects like dizziness or fatigue. While it shares a chemical class with the potent enzyme-inducer rifampin, rifaximin’s lack of systemic presence results in fewer drug interactions. However, clinicians must monitor for reduced effectiveness of typhoid vaccines and potential interactions with P-glycoprotein inhibitors or warfarin, which may alter systemic exposure or therapeutic levels.