Tamoxifen is a nonsteroidal agent and competitively binds to estrogen receptors (ER). This compound itself is a prodrug and it has a relatively little affinity for ER. However, tamoxifen can transform into active metabolites 4-hydroxytamoxifen and N-desmethyl-4-hydroxytamoxifen (endoxifen). Besides, these metabolites exhibit 30–100 times more affinity with the estrogen...