Last reviewed 2026-04-20 · How we verify

Fareston (TOREMIFENE)

Fareston works by binding to estrogen receptors in the body, which can help reduce the growth of breast cancer cells.

At a glance

Mechanism of action

Toremifene is 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. In general, however, nonsteroidal triphenylethylene derivatives are predominantly antiestrogenic in rats and humans and estrogenic in mice. In rats, toremifene causes regression of established dimethylbenzanthracene (DMBA)-induced mammary tumors. The antitumor effect of toremifene in breast cancer is believed to be mainly due to its antiestrogenic effects, i.e., its ability to compete with estrogen for binding sites in the cancer, blocking the growth-stimulating effects of estrogen in the tumor.

Approved indications

• Metastatic Breast Carcinoma

Boxed warnings

• WARNING: QT PROLONGATION FARESTON has been shown to prolong the QTc interval in a dose- and concentration-related manner [see Clinical Pharmacology (12.2) ] . Prolongation of the QT interval can result in a type of ventricular tachycardia called Torsade de pointes, which may result in syncope, seizure, and/or death. Toremifene should not be prescribed to patients with congenital/acquired QT prolongation, uncorrected hypokalemia or uncorrected hypomagnesemia. Drugs known to prolong the QT interval and strong CYP3A4 inhibitors should be avoided [see Warnings and Precautions (5.1) ] . WARNING: QT PROLONGATION FARESTON has been shown to prolong the QTc interval in a dose- and concentration-related manner [see Clinical Pharmacology (12.2) ] . Prolongation of the QT interval can result in a type of ventricular tachycardia called Torsade de pointes, which may result in syncope, seizure, and/or death. Toremifene should not be prescribed to patients with congenital/acquired QT prolongation, uncorrected hypokalemia or uncorrected hypomagnesemia. Drugs known to prolong the QT interval and strong CYP3A4 inhibitors should be avoided [see Warnings and Precautions (5.1) ] .

Common side effects

• Hot Flashes
• Sweating
• Nausea
• Vaginal Discharge
• Dizziness
• Edema
• Vomiting
• Vaginal Bleeding
• Cardiac Failure
• Myocardial Infarction
• Cataracts
• Dry Eyes

Drug interactions

• High Risk QT Prolonging Agents
• abarelix
• acetophenazine
• amiodarone
• amitriptyline
• apomorphine
• arsenic trioxide
• artemether
• astemizole
• atazanavir
• bepridil
• carbamazepine

Key clinical trials

• De-escalation Therapy in Stage I ER-Positive Breast Cancer: A Non-Inferiority Trial (PHASE3)
• Compare Adjuvant Monotherapy With Endocrine or Accelerated Partial Breast Irradiation After Lumpectomy (PHASE2)
• Efficacy and Safety of Dalpiciclib Plus Toremifene in the Treatment of Advanced First-line HR Positive and HER2 Negative Breast Cancer: a Multicenter, Single Arm, Exploratory Phase II Clinical Study (PHASE2)
• Stage I HER2 Positive Invasive Breast Cancer De-escalation Study(IRIS) (PHASE2)
• Adjuvant Pyrotinib and Capecitabine For HER2 Positive Micro Invasive Breast Cancer (PHASE2)
• Efficacy and Safety of Fluzoparib Combined With Adjuvant Endocrine Therapy for HR+/HER2- SNF3-subtype Early Breast Cancer (BCTOP-L-A01) (PHASE3)
• Prostate Cancer Prevention Study for Men With High Grade PIN (Prostatic Intraepithelial Neoplasia) (PHASE3)
• Comparative Evaluation of Efficacy and Safety of Toremifene, Tamoxifen, and Aromatase Inhibitor Plus Ovarian Function Suppression in Hormone Receptor-Positive Early Breast Cancer Among Non-Low-Risk Premenopausal Women: A Real-World Study

Primary sources

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