arimidex and Emblon Interactions

Interactions between arimidex(anastrozole) and Emblon (tamoxifen)

tamoxifen and anastrozole (Moderate Drug-Drug)

GENERALLY AVOID: Coadministration with tamoxifen may decrease the plasma concentrations of anastrozole. The mechanism of interaction has not been described. In one clinical trial, coadministration of tamoxifen (20 mg/day) and anastrozole (1 mg/day) in breast cancer patients resulted in decreased anastrozole plasma concentration by 27% compared to administration of anastrozole alone. In addition, at a median follow-up of 33 months, the combination did not demonstrate any efficacy benefit over tamoxifen therapy alone in all patients as well as in the hormone receptor-positive subpopulation, and this treatment arm was discontinued from the trial. The pharmacokinetics of tamoxifen and its pharmacologically active N-desmethyl metabolite were not affected.

MANAGEMENT: Concomitant use of tamoxifen and anastrozole should be avoided.