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Oral rifaximin 550 mg (Refero(®); Targaxan(®); Tixteller(®); Xifaxan(®)) twice daily, either alone or more commonly with medicines containing lactulose, is approved in several countries, including the UK, EU and USA, for use in adults with liver disease to reduce the recurrence of episodes of overt hepatic encephalopathy (HE). Rifaximin is a broad-spectrum antibacterial that acts locally in the gut to reduce intestinal flora, including ammonia-producing species, with hyperammonaemia considered to play a central role in the pathogenesis of HE. In a 6-month, multinational trial in patients with liver disease, rifaximin 550 mg twice daily (± lactulose) was an effective and well tolerated treatment for reducing the recurrence of HE episodes. At study end, rifaximin therapy significantly prolonged the time to the first breakthrough HE episode compared with placebo (± lactulose), irrespective of geographical region or baseline patient and disease characteristics. Rifaximin treatment also significantly reduced HE-related hospitalizations and improved health-related quality of life compared with placebo. Furthermore, the efficacy of rifaximin with or without lactulose in reducing the recurrence of overt HE episodes was maintained after up to 2.5 years of treatment, with no new safety signals arising during this period. This article reviews the pharmacology and therapeutic efficacy of rifaximin 550 mg twice daily in reducing the recurrence of overt HE episodes in adults with liver disease.