Distribution
Fidaxomicin is mainly confined to the gastrointestinal tract following oral administration. In selected patients (N=8) treated with DIFICID 200 mg twice daily for 10 days from controlled trials, fecal concentrations of fidaxomicin and OP-1118 obtained within 24 hours of the last dose ranged from 639-2710 μg/g and 213-1210 μg/g, respectively. In contrast, plasma concentrations of fidaxomicin and OP-1118 within the Tmax window (1-5 hours) ranged 2-179 ng/mL and 10-829 ng/mL, respectively.