With concomitant treatment with oestrogen-containing hormone-medications a decrease of both effects is possible (e.g. unreliable effect of the "Pill").
Concomitant use of tamoxifen with coumarin-type anticoagulants may result in an increase in the anticoagulant effect (marked prolongation of prothrombin times).
Concomitant use of tamoxifen with thrombocyte aggregation inhibitors may increase the bleeding tendency during a possible thrombocytopenic phase.
A close monitoring of the coagulation status is recommended.
Thromboembolic events have been reported more frequently when tamoxifen is given in combination with cytotoxic agents.
Concomitant bromocriptine therapy has been shown to elevate serum tamoxifen and its active metabolite N-demethyl tamoxifen.
The influence of food on the absorption of tamoxifen has not been studied. However, it is unlikely to influence steady-state kinetic parameters.