Approximately 24 patients will be entered into this study taking place in Canada. The aim of this study is to determine if an investigational drug is absorbed (taken up) in patients with C. difficile-associated diarrhea (CDAD). The investigational drug will be given in addition to current standard antibiotic treatment so that all patients will receive active medication. All study related care is provided including doctor visits, physical exams, laboratory tests, and study medication. The total length of participation is approximately 7 days.

Inclusion Criteria:

• 18 years of age or older
• The presence of CDAD at the time of enrollment with no other likely etiology for the diarrhea

Exclusion Criteria:

• > 72 hours of treatment with metronidazole, vancomycin, or other antibacterial therapy specifically targeting the current acute episode of CDAD
• Patient not considered sufficiently stable clinically to complete the study period