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PubChem
Name: Tamoxifen
PubChem Compound ID: 11451630
Description: 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.
Molecular formula: C26H29NO
Molecular weight: 374.533 g/mol
DrugBank
Identification
Name: Tamoxifen
Name (isomeric): DB00675
Drug Type: small molecule
Description: 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.
Synonyms:
Tamoxifen Citrate; Tamoxifenum [INN-Latin]; Tamoxifeno [INN-Spanish]; Trans-Tamoxifen; Tamoxifene [INN-French]
Brand: Nolvadex-D, Tamone, Crisafeno, Diemon, Novo-Tamoxifen, Zemide, Tamizam, Nourytam, PMS-Tamoxifen, Noltam, Apo-Tamox, Gen-Tamoxifen, Nolvadex, Tamofen, Retaxim, Tamoxasta, Citofen, Tamoxen, Valodex, Istubol, Oncomox, Kessar
Category: Estrogen Antagonists, Antineoplastic Agents, Hormonal, Bone Density Conservation Agents, Selective Estrogen Receptor Modulators
CAS number: 10540-29-1
Pharmacology
Indication: For the treatment of breast cancer.
Pharmacology: 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.
Mechanism 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 uptak...
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Biotransformation: 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.
Route of elimination: The drug is excreted mainly as polar conjugates, with unchanged drug and unconjugated metabolites accounting for less than 30% of the total fecal radioactivity.
Half Life: Distribution t1/2=7 to 14 hours; Elimination t1/2=5 to 7 days; Elimination t1/2 of N-desmethyl-tamoxifen=9-14 days.
Toxicity: Signs observed at the highest doses following studies to determine LD50 in animals were respiratory difficulties and convulsions.
Affected organisms: Humans and other mammals
Interactions
Drug interaction:
DiphenhydramineDiphenhydramine may decrease the therapeutic effect of Tamoxifen by decreasing the production of active metabolites. Consider alternate therapy.
MethadoneMethadone may decrease the therapeutic effect of Tamoxifen by decreasing the production of active metabolites. Consider alternate therapy.
MiconazoleMiconazole may decrease the therapeutic effect of Tamoxifen by decreasing the production of active metabolites. Concomitant therapy should be avoided.
CinacalcetCinacalcet may decrease the therapeutic effect of Tamoxifen by decreasing the production of active metabolites. Concomitant therapy should be avoided.
KetoconazoleKetoconazole may increase the serum concentration of Tamoxifen by decreasing its metabolism and clearance. Ketoconazole may also decrease the therapeutic effect of Tamoxifen by decreasing active metabolite production. Monitor for changes in the therapeutic/adverse effects of Tamoxifen if Ketoconazole is initiated, discontinued or dose changed.
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