Study determined to be infeasible.

The primary objective of this study is to characterize the steady state plasma

The primary objective of this study is to characterize the steady state plasma PK of rifaximin (550 mg BID) in subjects with severe hepatic impairment (MELD 19 to 25 and MELD >25), as well as healthy subjects with normal hepatic function.

Inclusion Criteria:

• Hepatically impaired subjects will be ≥18 years of age, have a diagnosis of liver cirrhosis and a MELD score of ≥19 at Screening. Note: At least 6 of the hepatically impaired subjects will have a MELD score of >25.

Exclusion Criteria:

• Subject has known allergy to rifaximin, rifampin, or other rifamycins, excipients and/or vehicles used in the formulation, or any other clinically significant allergies.
• Subject has participated in an investigational drug or device study within 30 days prior to Day 1 (Baseline).
• Subject has any concurrent illness (other than liver cirrhosis), disability or circumstance that may affect the interpretation of clinical data, could cause noncompliance with treatment or visits or otherwise contraindicates participation in this study in the opinion of the investigator.

7 days