Tamoxifen – Drugs Details

Tamoxifen is a selective estrogen receptor modulator used to treat estrogen receptor positive breast cancer, reduce the risk of invasive breast cancer following surgery, or reduce the risk of breast cancer in high risk women.

Background

Tamoxifen is a non-steroidal antiestrogen used to treat estrogen receptor positive breast cancers as well as prevent the incidence of breast cancer in high risk populations. Tamoxifen is used alone or as an adjuvant in these treatments. Tamoxifen may no longer be the preferred treatment for these types of cancers as patients generally have better survival, side effect profiles, and compliance with anastrozole.

Tamoxifen was granted FDA approval on 30 December 1977.

Pharmacodynamics

Tamoxifen is a selective estrogen receptor modulator that inhibits growth and promotes apoptosis in estrogen receptor positive tumors. It has a long duration of action as the active metabolite N-desmethyltamoxifen has a half life of approximately 2 weeks. It has a narrow therapeutic index as higher doses can lead to breathing difficulty or convulsions. Tamoxifen administration is also associated with an increased incidence of uterine malignancies.

Mechanism of action

Tamoxifen competitively inhibits estrogen binding to its receptor, which is critical for it’s activity in breast cancer cells. Tamoxifen leads to a decrease in tumor growth factor α and insulin-like growth factor 1, and an increase in sex hormone binding globulin. The increase in sex hormone binding globulin limits the amount of freely available estradiol.  These changes reduce levels of factors that stimulate tumor growth.

Tamoxifen has also been shown to induce apoptosis in estrogen receptor positive cells. This action is thought to be the result of inhibition of protein kinase C, which prevents DNA synthesis. Alternate theories for the apoptotic effect of tamoxifen comes from the approximately 3 fold increase in intracellular and mitochondrial calcium ion levels after administration or the induction of tumor growth factor β.

International/Other BrandsAdifen (Medicamerc) / Adopan (Sawai Seiyaku) / Bilem (Teva Int’l) / Caditam (Cadila) / Citofen / Crisafeno (LKM) / Doctamoxifene (Docpharma) / Ebefen (Ebewe) / Fenahex (Sandoz) / Genox (Merck Serono) / Gynatam (Biogalenic) / Istubal (AstraZeneca) / Mammonex (CP Pharmaceuticals) / Neophedan (Aspen Pharmacare) / Noltam / Nolvadex-D (AstraZeneca) / Novofen (Remedica) / Oncomox (Sun) / Tadex (Orion) / Tamifen (Medochemie) / Tamizam (Mithra) / Tamofen (Sanofi-Aventis) / Tamoneprin (Actavis) / Tamoplex (Pharmachemie) / Tamoxen (Ascent) / Tamoxilon (Celon) / Tamtero (Hetero) / Tecnotax (Zodiac) / Tomifen (Alkem) / Valodex / Zemide

Tamoxifen is in a class of medications known as antiestrogens. It blocks the activity of estrogen (a female hormone) in the breast. This may stop the growth of some breast tumors that need estrogen to grow.

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15. FDA Approved Drug Products: Tamoxifen Oral Tablets
16. FDA Approved Drug Products: Tamoxifen Oral Solution