Cimetidine does not increase the anticoagulant effect of phenprocoumon

In patients on oral warfarin, nicoumalone and phenindione an increase of the anticoagulant effect has been described during concomitant treatment with cimetidine. Therefore we have investigated the effect of cimetidine on the steady state dynamics of phenprocoumon in ten outpatients. No changes in the anticoagulant effect and the plasma phenprocoumon levels were observed during and after 2 weeks application of cimetidine. The data show that cimetidine does not interact with the metabolism of phenprocoumon in contrast to warfarin.