Version July 2025
Toremifene has been shown to prolong the QTc interval in a dose- and concentration-related manner. Prolongation of the QT interval can result in a type of ventricular tachycardia called torsades 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.
Note: Correct hypokalemia and hypomagnesemia prior to toremifene initiation.
Breast cancer, metastatic: Postmenopausal patients: Oral: 60 mg once daily, continue until disease progression or unacceptable toxicity (Ref).
Desmoid tumors: Aggressive fibromatosis, progressive (off-label use): Oral: 180 mg once daily until disease progression or unacceptable toxicity (Ref).
There are no dosage adjustments listed in the manufacturer’s labeling. However, pharmacokinetics in patients with kidney impairment are similar to those in patients with normal kidney function and dosage adjustment is unlikely to be necessary. No dosage adjustment necessary (Ref).
Hemodialysis: No need for dosage adjustment is expected (Ref).
There are no dosage adjustments provided in the manufacturer’s labeling. However, hepatic impairment increases the half-life of toremifene.
The following adjustment information has been recommended:
Mild to moderate impairment: No need for dosage adjustment is expected (Ref).
Severe impairment: Considering initiating with a 50% dose reduction and increase dose if tolerated (Ref).
Hypercalcemia: Manage as clinically indicated; discontinue toremifene for severe hypercalcemia.
Refer to adult dosing.
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.
>10%:
Dermatologic: Diaphoresis (20%)
Endocrine & metabolic: Hot flash (35%)
Gastrointestinal: Nausea (14%)
Genitourinary: Vaginal discharge (13%)
Hepatic: Increased serum alkaline phosphatase (8% to 19%), increased serum aspartate aminotransferase (5% to 19%)
1% to 10%:
Cardiovascular: Acute myocardial infarction (≤1%), cardiac arrhythmia (2%), edema (5%), heart failure (1%), pulmonary embolism (≤2%), thrombophlebitis (≤2%), thrombosis (≤2%)
Endocrine & metabolic: Hypercalcemia (≤3%)
Gastrointestinal: Vomiting (4%)
Genitourinary: Vaginal hemorrhage (2%)
Hepatic: Increased serum bilirubin (1% to 2%)
Nervous system: Cerebrovascular accident (≤2%), dizziness (9%), transient ischemic attacks (≤2%)
Ophthalmic: Cataract (10%), corneal disease (2%), diplopia (≤2%), dry eye syndrome (9%), glaucoma (≤2%), visual disturbance (≤2%), visual field defect (4%)
<1%: Cardiovascular: Angina pectoris
Frequency not defined:
Cardiovascular: Prolonged QT interval on ECG
Dermatologic: Alopecia, dermatitis, pruritus, skin discoloration
Gastrointestinal: Anorexia, constipation
Nervous system: Asthenia, depression, fatigue, lethargy, paresis, rigors, tremor, vertigo
Neuromuscular & skeletal: Arthritis
Ophthalmic: Corneal opacity (reversible; including corneal verticillata)
Respiratory: Dyspnea
Postmarketing:
Endocrine & metabolic: Hypertriglyceridemia
Genitourinary: Endometrial carcinoma, endometrial hyperplasia
Hematologic & oncologic: Leukopenia, polyp (uterine), thrombocytopenia, tumor flare
Hepatic: Hepatotoxicity (including hepatitis, jaundice, liver steatosis)
Known hypersensitivity to toremifene or any component of the formulation; congenital/acquired QT prolongation (long QT syndrome), uncorrected hypokalemia, uncorrected hypomagnesemia.
Concerns related to adverse effects:
• Bone marrow suppression: Leukopenia and thrombocytopenia have been reported rarely.
• Hepatotoxicity: Grades 3 and 4 transaminase increases and hyperbilirubinemia have been reported, including jaundice, hepatitis, and metabolic dysfunction associated steatotic liver disease.
• Hypercalcemia: Hypercalcemia may occur during the first weeks of treatment in patients with breast cancer with bone metastases. Medications that decrease renal calcium excretion (eg, thiazide diuretics) may increase the risk of hypercalcemia in patients receiving toremifene.
• QT prolongation: Toremifene may prolong the QT interval; QTc prolongation is dose-dependent and concentration-dependent. QT prolongation may lead to a form of ventricular tachycardia called torsades de pointes, which may result in syncope, seizure, and/or sudden death. Use with caution in patients with heart failure, hepatic impairment, or electrolyte abnormalities.
• Tumor flare: Tumor flair may occur during the first weeks of treatment in patients with breast cancer with bone metastases. Tumor flare consists of diffuse musculoskeletal pain and erythema with initial increased size of tumor lesions (which later regress). It is often accompanied by hypercalcemia and does not imply treatment failure or represent tumor progression.
• Uterine malignancy: Endometrial cancer, hypertrophy, hyperplasia, and uterine polyps have been reported. Long-term use of toremifene in patients with preexisting endometrial hyperplasia has not been established.
Disease-related concerns:
• Thromboembolic disease: Avoid toremifene use in patients with a history of thromboembolic disease.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Tablet, Oral:
Fareston: 60 mg
Generic: 60 mg
Yes
Tablets (Fareston Oral)
60 mg (per each): $52.00
Tablets (Toremifene Citrate Oral)
60 mg (per each): $45.83
Disclaimer: A representative AWP (Average Wholesale Price) price or price range is provided as reference price only. A range is provided when more than one manufacturer's AWP price is available and uses the low and high price reported by the manufacturers to determine the range. The pricing data should be used for benchmarking purposes only, and as such should not be used alone to set or adjudicate any prices for reimbursement or purchasing functions or considered to be an exact price for a single product and/or manufacturer. Medi-Span expressly disclaims all warranties of any kind or nature, whether express or implied, and assumes no liability with respect to accuracy of price or price range data published in its solutions. In no event shall Medi-Span be liable for special, indirect, incidental, or consequential damages arising from use of price or price range data. Pricing data is updated monthly.
Oral: Administer with or without food.
Hazardous agent (NIOSH 2024 [table 2]).
Use appropriate precautions for receiving, handling, storage, preparation, dispensing, transporting, administration, and disposal. Follow NIOSH and USP 800 recommendations and institution-specific policies/procedures for appropriate containment strategy (NIOSH 2023; NIOSH 2024; USP-NF 2020).
Note: Facilities may perform risk assessment of some hazardous drugs to determine if appropriate for alternative handling and containment strategies (USP-NF 2020). Refer to institution-specific handling policies/procedures.
Breast cancer, metastatic: Treatment of metastatic breast cancer in postmenopausal patients with estrogen receptor-positive tumors.
Desmoid tumors: Aggressive fibromatosis, progressive
Toremifene may be confused with ospemifene, raloxifene
Substrate of CYP1A2 (Minor), CYP3A4 (Major); Note: Assignment of Major/Minor substrate status based on clinically relevant drug interaction potential;
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the drug interactions program by clicking on the “Launch drug interactions program” link above.
Amisulpride (Oral): May increase QTc-prolonging effects of QT-prolonging Agents (Moderate Risk). Risk C: Monitor
Azithromycin (Systemic): QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Azithromycin (Systemic). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Chloroquine: QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Chloroquine. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Clofazimine: May increase serum concentration of CYP3A4 Substrates (High risk with Inhibitors). Risk C: Monitor
Clofazimine: QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Clofazimine. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
CYP2C9 Substrates (Narrow Therapeutic Index/Sensitive with Inhibitors): Toremifene may increase serum concentration of CYP2C9 Substrates (Narrow Therapeutic Index/Sensitive with Inhibitors). Risk C: Monitor
CYP3A4 Inducers (Moderate): May decrease serum concentration of Toremifene. CYP3A4 Inducers (Moderate) may decrease active metabolite exposure of Toremifene. Risk C: Monitor
CYP3A4 Inducers (Strong): May decrease serum concentration of Toremifene. CYP3A4 Inducers (Strong) may decrease active metabolite exposure of Toremifene. Risk X: Avoid
CYP3A4 Inhibitors (Moderate): May increase serum concentration of Toremifene. Risk C: Monitor
CYP3A4 Inhibitors (Strong): May increase serum concentration of Toremifene. Management: Use of toremifene with strong CYP3A4 inhibitors should be avoided if possible. If coadministration is necessary, monitor for increased toremifene toxicities, including QTc interval prolongation. Risk D: Consider Therapy Modification
Dabrafenib: Toremifene may increase QTc-prolonging effects of Dabrafenib. Dabrafenib may decrease serum concentration of Toremifene. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Also monitor for reduced toremifene efficacy. Risk C: Monitor
Domperidone: QT-prolonging Agents (Moderate Risk) may increase QTc-prolonging effects of Domperidone. Risk X: Avoid
Encorafenib: Toremifene may increase QTc-prolonging effects of Encorafenib. Encorafenib may decrease active metabolite exposure of Toremifene. Encorafenib may decrease serum concentration of Toremifene. Risk X: Avoid
Fexinidazole: May increase QTc-prolonging effects of QT-prolonging Miscellaneous Agents (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Fluoroestradiol F18: Coadministration of Estrogen Receptor Antagonists and Fluoroestradiol F18 may alter diagnostic results. Risk X: Avoid
Fluorouracil Products: QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Fluorouracil Products. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Fusidic Acid (Systemic): May increase serum concentration of CYP3A4 Substrates (High risk with Inhibitors). Management: Consider avoiding this combination if possible. If required, monitor patients closely for increased adverse effects of the CYP3A4 substrate. Risk D: Consider Therapy Modification
Gadobenate Dimeglumine: QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Gadobenate Dimeglumine. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Grapefruit Juice: May increase serum concentration of Toremifene. Risk X: Avoid
Halofantrine: QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Halofantrine. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Haloperidol: QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Haloperidol. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Inotuzumab Ozogamicin: QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Inotuzumab Ozogamicin. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Lefamulin: May increase QTc-prolonging effects of QT-prolonging CYP3A4 Substrates. Management: Do not use lefamulin tablets with QT-prolonging CYP3A4 substrates. Lefamulin prescribing information lists this combination as contraindicated. Risk X: Avoid
Levoketoconazole: QT-prolonging CYP3A4 Substrates may increase QTc-prolonging effects of Levoketoconazole. Levoketoconazole may increase serum concentration of QT-prolonging CYP3A4 Substrates. Risk X: Avoid
Lofexidine: QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Lofexidine. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Midostaurin: QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Midostaurin. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Ondansetron: QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Ondansetron. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Ospemifene: Selective Estrogen Receptor Modulators may increase adverse/toxic effects of Ospemifene. Ospemifene may also enhance adverse/toxic effects of other Selective Estrogen Receptor Modulators. Risk X: Avoid
Pentamidine (Systemic): QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Pentamidine (Systemic). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
Phenobarbital-Primidone: May decrease serum concentration of Toremifene. Risk C: Monitor
Pimozide: May increase QTc-prolonging effects of QT-prolonging Agents (Moderate Risk). Risk X: Avoid
Piperaquine: QT-prolonging Agents (Moderate Risk) may increase QTc-prolonging effects of Piperaquine. Risk X: Avoid
Posaconazole: May increase serum concentration of QT-prolonging CYP3A4 Substrates. Such increases may lead to a greater risk for proarrhythmic effects and other similar toxicities. Risk X: Avoid
Probucol: QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of Probucol. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
QT-prolonging Agents (Highest Risk): May increase QTc-prolonging effects of Toremifene. Management: Consider alternatives to this combination. Patients with other risk factors (eg, older age, female sex, bradycardia, hypokalemia, hypomagnesemia, heart disease, and higher drug concentrations) are likely at greater risk for these toxicities. Risk D: Consider Therapy Modification
QT-prolonging Antidepressants (Moderate Risk): May increase QTc-prolonging effects of QT-prolonging Miscellaneous Agents (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
QT-prolonging Antipsychotics (Moderate Risk): QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of QT-prolonging Antipsychotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
QT-prolonging Class IC Antiarrhythmics (Moderate Risk): QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of QT-prolonging Class IC Antiarrhythmics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
QT-Prolonging Inhalational Anesthetics (Moderate Risk): QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of QT-Prolonging Inhalational Anesthetics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
QT-prolonging Kinase Inhibitors (Moderate Risk): May increase QTc-prolonging effects of QT-prolonging Miscellaneous Agents (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
QT-prolonging Miscellaneous Agents (Moderate Risk): May increase QTc-prolonging effects of Toremifene. Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
QT-prolonging Moderate CYP3A4 Inhibitors (Moderate Risk): May increase QTc-prolonging effects of QT-prolonging Miscellaneous Agents (Moderate Risk). QT-prolonging Moderate CYP3A4 Inhibitors (Moderate Risk) may increase serum concentration of QT-prolonging Miscellaneous Agents (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
QT-prolonging Quinolone Antibiotics (Moderate Risk): QT-prolonging Miscellaneous Agents (Moderate Risk) may increase QTc-prolonging effects of QT-prolonging Quinolone Antibiotics (Moderate Risk). Management: Monitor for QTc interval prolongation and ventricular arrhythmias when these agents are combined. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk C: Monitor
QT-prolonging Strong CYP3A4 Inhibitors (Highest Risk): Toremifene may increase QTc-prolonging effects of QT-prolonging Strong CYP3A4 Inhibitors (Highest Risk). QT-prolonging Strong CYP3A4 Inhibitors (Highest Risk) may increase serum concentration of Toremifene. Management: Consider alternatives to this combination. If combined, monitor for QTc interval prolongation and ventricular arrhythmias. Patients with additional risk factors for QTc prolongation may be at even higher risk. Risk D: Consider Therapy Modification
QT-prolonging Strong CYP3A4 Inhibitors (Moderate Risk): Toremifene may increase QTc-prolonging effects of QT-prolonging Strong CYP3A4 Inhibitors (Moderate Risk). QT-prolonging Strong CYP3A4 Inhibitors (Moderate Risk) may increase serum concentration of Toremifene. Management: Avoid concomitant use of toremifene and strong CYP3A4 inhibitors that prolong the QTc interval whenever possible. If combined, monitor patients for toremifene toxicities including QTc prolongation and TdP. Risk D: Consider Therapy Modification
Sertindole: May increase QTc-prolonging effects of QT-prolonging Agents (Moderate Risk). Risk X: Avoid
Sugammadex: Toremifene may decrease therapeutic effects of Sugammadex. Risk C: Monitor
Thiazide and Thiazide-Like Diuretics: May increase hypercalcemic effects of Toremifene. Risk C: Monitor
Thioridazine: QT-prolonging Agents (Moderate Risk) may increase QTc-prolonging effects of Thioridazine. Risk X: Avoid
Grapefruit and grapefruit juice may increase toremifene levels. Management: Avoid grapefruit products.
Toremifene is only approved for use in postmenopausal patients; however, if prescribed in premenopausal patients, effective nonhormonal contraception should be used.
Based on the mechanism of action and data from animal reproduction studies, in utero exposure to toremifene may cause fetal harm.
It is not known if toremifene is present in breast milk. Due to the potential for serious adverse reactions in the breastfed infant, the manufacturer recommends a decision be made to discontinue breastfeeding or to discontinue the drug, taking into account the importance of treatment to the mother.
Avoid grapefruit and grapefruit juice.
CBC with differential (periodically; particularly leukocyte and platelet counts in patients with leukopenia and thrombocytopenia), electrolytes (magnesium and potassium prior to and periodically during treatment; calcium periodically), hepatic function tests (periodically). Obtain ECG (baseline and periodically during treatment) in patients at risk for QT prolongation. In patients with bone metastases, monitor closely for hypercalcemia during the first few weeks of treatment. Baseline and annual gynecological exams (patients at high risk for endometrial cancer should be closely monitored). Monitor for signs/symptoms of uterine disorders (bleeding, discharge, pelvic pain/pressure) and tumor flare. Monitor adherence.
Cardiovascular monitoring for patients with breast cancer: Comprehensive assessment prior to treatment including a history and physical examination, screening for cardiovascular disease risk factors such as hypertension, diabetes, dyslipidemia, obesity, and smoking; estimate 10-year cardiovascular disease risk in patients without cardiovascular disease at baseline; assess cardiovascular risk annually in patients with a high 10-year risk (ASCO [Armenian 2017]; ESC [Lyon 2022]).
Toremifene is a nonsteroidal triphenylethylene derivative with potent antiestrogenic properties (also has estrogenic effects) that competitively binds to estrogen receptors on tumors and inhibits the growth stimulating effects of estrogen.
Absorption: Well absorbed
Distribution: Vd: 580 L
Protein binding, plasma: >99.5%, primarily to albumin
Metabolism: Extensively hepatic, principally by CYP3A4 to N-demethyltoremifene (a weak antiestrogen)
Bioavailability: Not affected by food
Half-life elimination: Toremifene: ~5 days, ~7 days (females > 60 years); N-demethyltoremifene: 6 days
Time to peak, serum: ≤3 hours
Excretion: Primarily feces; urine (~10%) during a 1-week period
Hepatic function impairment: The mean elimination half-life was increased by less than 2-fold in patients with cirrhosis or fibrosis.
Older adult: In a small study, the elimination half-life was prolonged (4.2 vs 7.2 days) and Vd increased (457 vs 627 L) in females ≥60 years of age, compared to younger males.
