In both Japanese and Caucasian subjects, fidaxomicin showed minimal systemic absorption following oral administration.

Plasma concentrations of fidaxomicin and its main metabolite OP-1118 were in the ng/mL range, with the maximum plasma concentration and area under the concentration–time curve values higher in Japanese subjects than in Caucasian subjects.

The drug was mainly excreted in feces. Fidaxomicin was safe and well-tolerated in both subject groups.