Tamoxifen

In medicine, tamoxifen is "one of the selective estrogen receptor modulators with tissue-specific activities. Tamoxifen acts as an anti-estrogen (inhibiting agent) in the mammary tissue, but as an estrogen (stimulating agent) in cholesterol metabolism, bone density, and cell proliferation in the endometrium.

Metabolism
Tamoxifen is metabolized in the liver by cytochrome P-450 CYP2D6 to active metabolites.

Drug interactions
Paroxetine may increase death from breast cancer among women taking tamoxifen due to inhibiting metabolism of tamoxifen to its active metabolite by cytochrome P-450 CYP2D6.