Rifaxiheal 400 mg is an antibiotic containing rifaximin, used mainly to treat hepatic encephalopathy, infectious diarrhea, and irritable bowel syndrome with diarrhea (IBS-D). It works by killing harmful bacteria in the intestines, reducing symptoms and preventing recurrence. It is taken orally, with or without food, as prescribed. Common side effects include nausea, headache, dizziness, and rash. Proper use improves brain function and digestive health.