This study is being conducted to see if an investigational drug, named Rifaximin SSD-40IR may help delay the first episode of overt hepatic encephalopathy (OHE) requiring hospitalization in patients with liver cirrhosis, as well as how safe the drug is for humans. Hepatic encephalopathy is a nervous system disorder caused by a buildup of toxins in the blood when the liver does not work properly.
   
An investigational/experimental drug is one that is currently being tested and has not yet been approved by the U.S. Food and Drug Administration (FDA). Experimental drugs such as Rifaximin SSD tablets may be tested in research studies such as this one.
   
Participants will be randomly assigned to receive Rifaximin SSD-40IR twice daily or placebo. A placebo looks like Rifaximin SSD-40IR, but contains no active drug/ingredient. Participants will have a 50% chance of receiving Rifaximin SSD-40IR and a 50% chance of receiving placebo, like flipping a coin. In this study, neither the participant nor the study doctor will know what study treatment participants are receiving.
    
Participation in this study will last approximately 80 weeks.