Comparative pharmacokinetics of coumarin anticoagulants XXXV: Examination of possible pharmacokinetic interaction between (R)-(+)- and (S)-(--)-warfarin in humans.

The elimination kinetics and anticoagulant effect produced by single 1.5-mg/kg doses of (R)-(+(-, (S)-(--)-, and racemic warfarin were determined in 10 healthy men. The results obtained in experiments with the individual enantiomers were used to predict the elimination kinetics and anticoagulant effect of racemic warfarin, assuming that there is no interaction between the two enantiomers. These predictions were compared to experimental results, and no significant differences were observed. This finding suggests that there are no pronounced pharmacokinetic or pharmacodynamic interactions between single large doses of (R)-(+)- and (S)-(--)-warfarin in humans.