Hi. Welcome to HCM.Xifaxan contains Rifaximin ia semi-synthetic antibiotic used for treating traveler s diarrhea and hepatic encephalopathy. It is active against Escherichia coli bacterial strains. Hepatic encephalopathy is a serious neurologic complication of advanced liver disease that affects the brain. It is believed to be caused by the absorption of ammonia and other chemicals produced by bacteria in the intestine. It is believed that rifaximin prevents and treats hepatic encephalopathy by reducing the intestinal bacteria that produce ammonia. Going with the dosage which your doc has prescribed u (550 mg), i think its for hepatic encephalopathy. I would suggest u not to skip the two doses. if u do so it will not be of any benefit to u. It highly recommended that people suffering from Hepatic encephalopathy to take two doses. If u miss any dose take as soon as u remember, but dont overdose yourself to make up the missed dose. All the best. Wish u good health