ARIMIDEX does not work in Women of all ages with breast most cancers that have not undergone menopause (premenopausal Girls).tamoxifen. You should not consider ARIMIDEX if you are taking tamoxifen. Having ARIMIDEX with tamoxifen may perhaps lower the amount of ARIMIDEX in your blood and may induce ARIMIDEX not to operate likewise.etant précedemmen