The clearance of R-warfarin is generally half that of S-warfarin, thus as the volumes of distribution are similar, the half-life of R-
warfarin is longer than that of S-
warfarin. The half-life of R-
warfarin ranges from 37 to 89 hours, while that of S-warfarin ranges from 21 to 43 hours. Studies with radiolabeled drug have demonstrated that up to 92% of the orally administered dose is recov-ered in urine. Very little warfarin is excreted unchanged in urine.