Tamoxifen is classified as a SERM and this also refers to its mechanism. This means it is an antagonist for estrogen receptors in some tissues, while an agonist at others. It has selective effects.
This drug competitively binds to and antagonizes estrogen binding to estrogen receptors on tumor cells. Thus, this drug is only helpful in estrogen receptor positive (ER+) breast cancers.
Tamoxifen is used in estrogen receptor (ER) positive breast cancer.
This is a positive effect of the drug. As it is a selective estrogen receptor modulator, it's an agonist for estrogen receptors at some places (bone) and an antagonist at others (breast). This increases estrogen binding to the bone, preventing osteoclast binding and osteoporosis.
Tamoxifen is a partial agonist for estrogen receptors on endometrial tissue, leading to endometrial hyperplasia and an increased risk for endometrial cancer.
Though the pathophysiology is not completely understood, high levels of estrogen has been shown to be a risk factor for venous thromboembolism (VTE).
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