Brands, Medical Use, Clinical Data
- Antineoplastic Agents
- Selective Estrogen Receptor Modulators
Brands / Synonyms
Acapodene; Fareston; Farestone; Toremifene Base; Toremifeno [Spanish]; Toremifenum [Latin]; Z-Toremifene
For the treatment of metastatic breast cancer in postmenopausal women with estrogen receptor-positive or receptor-unknown tumors
Toremifene is an antineoplastic hormonal agent primarily used in the treatment of advanced breast cancer. Toremifene is a nonsteroidal agent that has demonstrated potent antiestrogenic properties in animal test systems. The antiestrogenic effects may be related to its ability to compete with estrogen for binding sites in target tissues such as breast. Toremifene inhibits the induction of rat mammary carcinoma induced by dimethylbenzanthracene (DMBA) and causes the regression of already established DMBA-induced tumors. In this rat model, Toremifene appears to exert its antitumor effects by binding the estrogen receptors. In cytosols derived from human breast adenocarcinomas, Toremifene competes with estradiol for estrogen receptor protein.
Mechanism of Action
Toremifene is a nonsteroidal triphenylethylene derivative. Toremifene binds to estrogen receptors and may exert estrogenic, antiestrogenic, or both activities, depending upon the duration of treatment, animal species, gender, target organ, or endpoint selected. The antitumor effect of toremifene in breast cancer is believed to be mainly due to its antiestrogenic effects, ie, its ability to compete with estrogen for binding sites in the cancer, blocking the growth-stimulating effects of estrogen in the tumor.
Biotrnasformation / Drug Metabolism
Mainly by CYP3A4
FARESTON is contraindicated in patients with known hypersensitivity to the drug.
Drugs that decrease renal calcium excretion, eg, thiazide diuretics, may increase the risk of hypercalcemia in
patients receiving FARESTON. There is a known interaction between antiestrogenic compounds of the triphenylethylene
derivative class and coumarin-type anticoagulants (eg, warfarin), leading to an increased prothrombin time. When
concomitant use of anticoagulants with FARESTON is necessary, careful monitoring of the prothrombin time is
Cytochrome P450 3A4 enzyme inducers, such as phenobarbital, phenytoin, and carbamazepine increase the rate of
toremifene metabolism, lowering the steady-state concentration in serum. Metabolism of toremifene may be inhibited by
drugs known to inhibit the CYP3A4-6 enzymes. Examples of such drugs are ketoconazole and similar antimycotics as well
as erythromycin and similar macrolides. This interaction has not been studied and its clinical relevance is