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Product Name:
CAS Number:
For the treatment of breast cancer.
Mode of Action:

Tamoxifen binds to estrogen receptors (ER), inducing a conformational change in the receptor. This results in a blockage or change in the expression of estrogen dependent genes. The prolonged binding of tamoxifen to the nuclear chromatin of these results in reduced DNA polymerase activity, impaired thymidine utilization, blockade of estradiol uptake, and decreased estrogen response. It is likely that tamoxifen interacts with other coactivators or corepressors in the tissue and binds with different estrogen receptors, ER-alpha or ER-beta, producing both estrogenic and antiestrogenic effects.


Tamoxifen belongs to a class of drugs called selective estrogen receptor modulators (SERMs), which have both estrogenic and antiestrogenic effects. Tamoxifen has the same nucleus as diethylstilbestrol but possesses an additional side chain (trans isomer) which accounts for its antiestrogenic activity.


Hepatic. Tamoxifen is extensively metabolized after oral administration. N-Desmethyl-tamoxifen is the major metabolite found in plasma. N-Desmethyl-tamoxifen activity is similar to tamoxifen. 4-hydroxy-tamoxifen and a side chain primary alcohol derivative of tamoxifen have been identified as minor metabolites in plasma. 4-Hydroxy-tamoxifen formation is catalyzed mainly by cytochrome P450 (CYP) 2D6, and also by CYP2C9 and 3A4. At high tamoxifen concentrations, CYP2B6 also catalyzes 4-hydroxylation of the parent drug. 4-Hydroxy-tamoxifen possesses 30- to 100-times greater affinity for the estrogen receptor and 30- to 100-times greater potency at inhibiting estrogen-dependent cell proliferation compared to tamoxifen.


Signs observed at the highest doses following studies to determine LD50 in animals were respiratory difficulties and convulsions.

(2-{4-[(1Z)-1, 2-diphenylbut-1-en-1-yl]phenoxy}ethyl)dimethylamine
DB00675 (APRD00123)
Molecular Mass:
Tamoxifen Citrate Tamoxifene [INN-French] Tamoxifeno [INN-Spanish] Tamoxifenum [INN-Latin] Trans-Tamoxifen
AHFS Code:
General Reference:
General Reference:

  1. Jordan VC: Tamoxifen (ICI46, 474) as a targeted therapy to treat and prevent breast cancer. Br J Pharmacol. 2006 Jan;147 Suppl 1:S269-76. Pubmed
  2. Jordan VC: Fourteenth Gaddum Memorial Lecture. A current view of tamoxifen for the treatment and prevention of breast cancer. Br J Pharmacol. 1993 Oct;110(2):507-17. Pubmed
  3. Howell A, Cuzick J, Baum M, Buzdar A, Dowsett M, Forbes JF, Hoctin-Boes G, Houghton J, Locker GY, Tobias JS: Results of the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial after completion of 5 yearsê adjuvant treatment for breast cancer. Lancet. 2005 Jan 1-7;365(9453):60-2. Pubmed
  4. Steiner AZ, Terplan M, Paulson RJ: Comparison of tamoxifen and clomiphene citrate for ovulation induction: a meta-analysis. Hum Reprod. 2005 Jun;20(6):1511-5. Epub 2005 Apr 21. Pubmed
  5. van Bommel EF, Hendriksz TR, Huiskes AW, Zeegers AG: Brief communication: tamoxifen therapy for nonmalignant retroperitoneal fibrosis. Ann Intern Med. 2006 Jan 17;144(2):101-6. Pubmed

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