Toremifene is an oral selective estrogen receptor modulator (SERM): a drug that blocks estrogen in some tissues, such as breast tumors, while acting like estrogen in others, such as the liver and bone. It was approved in the US in 1997 as Fareston for metastatic breast cancer in postmenopausal women. Chemically it is tamoxifen with one added chlorine atom, and in breast cancer trials it performed about the same as tamoxifen.
Outside oncology, toremifene has been tested in men to protect bone during prostate cancer hormone therapy and to prevent prostate cancer, and it is sold informally as a “post-cycle therapy” (PCT) drug. None of these male uses is FDA-approved, and no controlled trial has tested it for recovery after anabolic steroid use. The label carries a boxed warning for QT prolongation, a heart-rhythm effect that grows with dose.
This page summarizes what the FDA label, clinical trials and regulators report. It is for education only and is not medical advice.
| Property | Detail |
|---|---|
| Drug class | Nonsteroidal SERM (triphenylethylene derivative, chlorinated tamoxifen analog) |
| Brand / approval | Fareston (NDA 020497), approved May 29, 1997; brand now discontinued in the US; generic tablets marketed |
| Route | Oral tablet |
| Strength | 60 mg toremifene (as 88.5 mg toremifene citrate) |
| Labeled dose | 60 mg once daily, until disease progression |
| Half-life (label) | Elimination half-life about 5 days; main metabolite N-demethyltoremifene about 6 days |
| Key mechanism fact | Metabolized mainly by CYP3A4; the label names no CYP2D6 activation step, unlike tamoxifen |
| Boxed warning | Dose- and concentration-related QT prolongation |
| US status | Prescription only; not listed as a controlled substance in 21 CFR 1308.13 |
| WADA status | Prohibited at all times (S4.2, anti-estrogenic substances) |
What it is
Toremifene’s chemical name is 2-[p-[(Z)-4-chloro-1,2-diphenyl-1-butenyl]phenoxy]-N,N-dimethylethylamine. The free base is C₂₆H₂₈ClNO, molecular weight 406.0 g/mol (PubChem). Tablets contain the citrate salt (598.1 g/mol), so each tablet holds 88.5 mg of toremifene citrate, equivalent to 60 mg of toremifene (Fareston label).
Its structure is identical to tamoxifen except for a chlorine atom on the side chain (Roelfsema et al., J Endocr Soc 2018). It belongs to the same triphenylethylene family as tamoxifen and clomiphene. Raloxifene is another SERM; one male infertility study compared all three (see below).
How it works
The label describes toremifene as binding estrogen receptors and acting as an estrogen, an antiestrogen or both, depending on species, tissue and endpoint. Its anticancer effect is thought to come mainly from blocking estrogen’s growth signal in the tumor. The label also reports estrogen-like effects in postmenopausal women, including lower FSH and LH (Fareston label).
The general SERM tissue map (breast, pituitary, uterus, liver) is explained on the tamoxifen page. The points below are where toremifene’s own data stand out:
| Tissue or system | Toremifene finding | Source |
|---|---|---|
| Breast tumor | Blocks estrogen; response rates similar to tamoxifen | Label; Cochrane 2012 |
| Liver | Estrogen-like: SHBG and IGFBP-1 rise, IGF-1 falls ≈20% | Roelfsema 2018 |
| Bone (men on ADT) | Estrogen-like: bone density rises, vertebral fractures fall | Smith 2008, 2010 |
| Lipids (men on ADT) | LDL and triglycerides fall, HDL slightly up vs placebo | Smith 2008 |
| Uterus | Endometrial hyperplasia, polyps and cancer reported | Label |
| Heart rhythm | QTc prolongation, dose-related | Label |
Pharmacokinetics
From the Fareston label (DailyMed):
| Parameter | Value |
|---|---|
| Absorption | Well absorbed; not affected by food |
| Time to peak | Within 3 hours |
| Dose linearity | Linear for single doses of 10–680 mg |
| Time to steady state | About 4–6 weeks |
| Protein binding | Over 99.5%, mainly albumin |
| Volume of distribution | About 580 L |
| Elimination half-life | About 5 days (distribution half-life about 4 hours) |
| Main metabolite | N-demethyltoremifene, half-life about 6 days, 2–4 times the parent level at steady state |
| Excretion | Mainly feces as metabolites; about 10% in urine over 1 week; enterohepatic recirculation slows elimination |
A few label details matter in practice:
- CYP3A4 drives metabolism. Ketoconazole raised toremifene exposure (AUC) 2.9-fold in 18 healthy subjects. Strong inducers such as rifampin, carbamazepine and St. John’s Wort lower levels.
- Self-induction. Over 17 days of dosing, toremifene exposure fell about 14% and N-demethyltoremifene exposure rose about 80%, consistent with toremifene inducing its own CYP3A4 metabolism.
- Age and liver. In elderly women the half-life was 7.2 days vs 4.2 days in young men. Liver impairment lengthened it by less than twofold.
Because the metabolism runs mainly through CYP3A4, toremifene does not depend on the CYP2D6 activation step that makes tamoxifen’s effect vary by genotype. In a retrospective Chinese cohort of 192 breast cancer patients, liver and gynecological adverse events were more frequent on tamoxifen than on toremifene among CYP2D6 extensive metabolizers, but not among intermediate metabolizers (Zhou et al., Int J Cancer 2022).
In anti-doping excretion studies, a single 60 mg dose in three women produced 15 urinary metabolites, most detectable for more than 10 days (Mazzarino et al., Anal Bioanal Chem 2011).
The label half-life of about 5 days matches the 120 hours listed for this compound in the library.
Approved medical use
The label’s only indication is metastatic breast cancer in postmenopausal women whose tumors are estrogen-receptor positive or of unknown receptor status. The dose is 60 mg once daily, generally continued until the disease progresses. There is no pediatric indication, and the label lists no approved use in men (Fareston label).
The original Fareston application (NDA 020497) was approved on May 29, 1997 as a new molecular entity. Drugs@FDA now lists the brand as discontinued (Drugs@FDA), while generic 60 mg tablets remain on the market (generic toremifene label). In June 2026 FDA determined that Fareston 60 mg was not withdrawn from sale for reasons of safety or effectiveness, which allows generics to keep referencing it (91 FR 34634).
What the research shows
Metastatic breast cancer vs tamoxifen
Approval rested on three randomized trials in postmenopausal women with receptor-positive or unknown metastatic breast cancer (Fareston label):
| Trial | Arms (n) | Response rate | Median time to progression | Median survival |
|---|---|---|---|---|
| North American | Toremifene 60 mg (221) vs tamoxifen 20 mg (215) | 21.3% vs 19.1% | 5.6 vs 5.8 months | 33.6 vs 34.0 months |
| Eastern European | Toremifene 60 mg (157) vs tamoxifen 40 mg (149) | 20.4% vs 20.8% | 4.9 vs 5.0 months | 25.4 vs 23.4 months |
| Nordic | Toremifene 60 mg (214) vs tamoxifen 40 mg (201) | 31.3% vs 37.3% | 7.3 vs 10.2 months | 33.0 vs 38.7 months |
Two trials showed similar results on every endpoint. The Nordic trial showed a longer time to progression on tamoxifen (hazard ratio 0.80, 95% CI 0.64–1.00), with no significant survival difference. Higher toremifene doses (200 and 240 mg/day) were not better than 60 mg. In the North American trial, 200 mg/day raised nausea to 37% vs 26% on 60 mg (Hayes et al., J Clin Oncol 1995).
A Cochrane review pooled 7 randomized trials with 2,061 patients (Mao et al., Cochrane 2012):
| Outcome | Toremifene vs tamoxifen |
|---|---|
| Objective response rate | 25.8% vs 26.9% (RR 1.02, 95% CI 0.88–1.18) |
| Time to progression | HR 1.08 (95% CI 0.94–1.24) |
| Overall survival | HR 1.02 (95% CI 0.86–1.20) |
| Headache | Less frequent on toremifene (RR 0.14, 95% CI 0.03–0.74) |
The reviewers concluded the two drugs are equally effective in first-line treatment.
Early breast cancer (adjuvant use)
A meta-analysis of four randomized adjuvant trials (1,890 patients on toremifene, 1,857 on tamoxifen) found no significant difference in overall survival (RR 1.07, 95% CI 0.97–1.19) or disease-free survival (RR 1.05, 95% CI 0.95–1.17). Rates of blood clots, stroke, endometrial polyps and endometrial cancer were also similar (Zhou et al., Breast Cancer Res Treat 2011). Adjuvant use is not a labeled US indication.
Bone, lipids and fractures in men on androgen deprivation
Androgen deprivation therapy (ADT) for prostate cancer causes bone loss. A phase 3 trial randomized men on ADT (median age 76) to toremifene 80 mg/day or placebo for 2 years (Smith et al., J Urol 2010):
| Outcome at 2 years | Toremifene (n = 646) | Placebo (n = 638) |
|---|---|---|
| New vertebral fractures | 2.5% | 4.9% |
| Lumbar spine bone density vs placebo | +2.3% (95% CI 1.6–3.1) | — |
| Total hip bone density vs placebo | +1.9% (95% CI 1.3–2.4) | — |
| Venous thromboembolism | 2.6% | 1.1% |
| Hot flushes | 3.9% | 5.3% |
The 50% relative reduction in vertebral fractures was borderline (95% CI −1.5 to 75.0, p = 0.05). Bone turnover markers fell significantly. Interim analyses of the same trial reported early bone-density results in 197 men and lipid results in 188 men (Smith et al., J Urol 2008; Smith et al., J Clin Oncol 2008):
| Change from baseline at 12 months | Toremifene | Placebo |
|---|---|---|
| LDL cholesterol | −8.2% | +0.8% |
| HDL cholesterol | +0.5% | −4.9% |
| Triglycerides | −13.2% | +6.9% |
| Total cholesterol | −8.1% | −1.0% |
This is the opposite direction from oral anabolic steroids such as oxandrolone, which lower HDL. The lipid data come from older men on ADT, however, not from men with normal or high androgen levels. The 80 mg dose used in these trials is above the labeled 60 mg dose, and bone protection in men is not a labeled indication.
Prostate cancer prevention
A phase 2b trial randomized 514 men with high-grade prostatic intraepithelial neoplasia (HGPIN, a precancerous biopsy finding) to toremifene 20, 40 or 60 mg/day or placebo for 12 months. The 20 mg dose lowered cumulative cancer detection to 24.4% vs 31.2% on placebo (Price et al., J Urol 2006).
The larger phase 3 follow-up did not confirm this. Among 1,590 men randomized to toremifene 20 mg or placebo for 3 years, cancer was found in 32.3% vs 34.7%, with no difference in cancer-free survival (p = 0.39) and no subgroup benefit (Taneja et al., J Clin Oncol 2013).
Hormones in men
Data on toremifene and the male hormonal axis are limited and do not show a consistent testosterone-raising effect:
| Study | Design | Dose and duration | Main hormonal findings |
|---|---|---|---|
| Roelfsema et al., J Endocr Soc 2018 | Double-blind placebo-controlled crossover, 20 healthy men aged 50–80 | 60 mg/day for about 10 days | LH 5.6 vs 5.9 IU/L (not significant); total testosterone 402 vs 455 ng/dL; free testosterone unchanged (7.42 vs 7.61 ng/dL); SHBG 43 vs 52 nmol/L; IGF-1 108 vs 85 µg/L |
| Farmakiotis et al., Fertil Steril 2007 | Uncontrolled, 100 subfertile men with idiopathic oligozoospermia | 60 mg/day for 3 months | FSH, testosterone, SHBG and inhibin B rose; sperm count, motility and morphology improved; 22 partners became pregnant within 2 months |
| Tsourdi et al., Fertil Steril 2009 | Comparison in 284 subfertile men | Tamoxifen 20 mg, toremifene 60 mg or raloxifene 60 mg daily | Gonadotropins rose with all three; the rise was larger with tamoxifen and toremifene than with raloxifene |
In the controlled crossover study, the rise in total testosterone was fully explained by higher SHBG (the protein that binds testosterone in blood); free and bioavailable testosterone did not change. The infertility studies had no placebo group. Toremifene is not approved for male infertility or low testosterone, and the clomiphene and enclomiphene pages cover SERMs with more male hormonal data.
Gynecomastia and recovery after anabolic steroid use
We found no randomized trial of toremifene for gynecomastia (male breast tissue growth) and no controlled trial of toremifene for recovery of the hormonal axis after anabolic steroid use. The gynecomastia trial evidence for SERMs is mainly with tamoxifen and is summarized on the tamoxifen page.
About “toremifene is the gentler PCT SERM.” Online claims that toremifene is a safer or more liver-friendly alternative to tamoxifen for post-cycle use are not backed by trials in that setting. In the label’s North American trial, AST elevations were 5% on toremifene vs 2% on tamoxifen, and alkaline phosphatase elevations 19% vs 11%. Toremifene also carries a boxed warning for QT prolongation (below).
Side effects and risks
Boxed warning: QT prolongation
Toremifene lengthens the QTc interval (the heart’s corrected electrical recovery time) in a dose- and concentration-related way. A long QT can lead to torsade de pointes, a dangerous ventricular rhythm that may cause fainting, seizures or death. In a randomized study of healthy men aged 18–45, measured at steady state on day 5 (Fareston label):
| Daily dose | Mean QTc increase vs placebo (90% CI) | QTc rise over 60 ms | QTc over 500 ms |
|---|---|---|---|
| 20 mg (n = 47) | 7 ms (0.9–13.6) | 0 | 0 |
| 80 mg (n = 47) | 26 ms (21.1–31.2) | 2 (4.3%) | 0 |
| 300 mg (n = 48) | 65 ms (60.1–69.2) | 43 (89.6%) | 5 (10.4%) |
The 300 mg dose was chosen to mimic exposure after a drug interaction or liver impairment. Because a strong CYP3A4 inhibitor nearly triples toremifene exposure, the label says to avoid these drugs and other QT-prolonging drugs. In a European pharmacovigilance analysis, SERMs (tamoxifen and toremifene) had more reports of long QT and torsade de pointes than aromatase inhibitors (reporting odds ratio for long QT 4.2) (Grouthier et al., Heart 2018).
Common side effects
Rates in the North American trial, from the label (Fareston label). The first six rows are effects judged drug-related; the eye findings came from scheduled eye exams:
| Effect | Toremifene 60 mg (n = 221) | Tamoxifen 20 mg (n = 215) |
|---|---|---|
| Hot flashes | 35% | 30% |
| Sweating | 20% | 17% |
| Nausea | 14% | 15% |
| Vaginal discharge | 13% | 16% |
| Dizziness | 9% | 7% |
| Edema | 5% | 5% |
| Cataracts | 10% | 7.5% |
| Dry eyes | 9% | 7.5% |
About 1% of 592 toremifene patients across the three trials stopped because of side effects.
Liver
The label warns of hepatotoxicity, including grade 3–4 transaminase rises, jaundice, hepatitis and non-alcoholic fatty liver disease, and advises periodic liver tests. Elevated AST and alkaline phosphatase were common in all three trials, on both drugs.
Blood clots and stroke
The label says patients with a history of thromboembolic disease should generally not be treated. In the male ADT trial, venous thromboembolism occurred in 2.6% on toremifene 80 mg vs 1.1% on placebo, 13 of the 17 cases in the first year (Smith et al., J Urol 2010). Against tamoxifen in adjuvant trials, clot and stroke rates were similar (Zhou et al., Breast Cancer Res Treat 2011).
Uterus, calcium and blood counts
- Uterus: endometrial cancer, hyperplasia and polyps have been reported; the label calls for baseline and annual gynecological exams.
- Hypercalcemia and tumor flare: can occur in the first weeks in women with bone metastases.
- Blood counts: low white cells and platelets have been reported rarely; the label advises periodic blood counts, calcium and liver tests.
Interactions
| Interacting drug or food | Effect | Label advice |
|---|---|---|
| Strong CYP3A4 inhibitors (ketoconazole, clarithromycin, ritonavir, grapefruit) | Toremifene exposure up to 2.9-fold | Avoid |
| QT-prolonging drugs (class IA and III antiarrhythmics, some antipsychotics, antidepressants, antibiotics, ondansetron) | Additive QT prolongation | Avoid or monitor ECG |
| Strong CYP3A4 inducers (rifampin, carbamazepine, phenytoin, dexamethasone, St. John’s Wort) | Lower toremifene levels | Avoid |
| Warfarin, phenytoin (CYP2C9 substrates) | Toremifene is a weak CYP2C9 inhibitor | Use with caution and monitor |
| Thiazide diuretics | Higher risk of hypercalcemia | Caution |
Who should not use it
The label contraindicates toremifene in people with:
- known hypersensitivity to the drug;
- congenital or acquired QT prolongation (long QT syndrome);
- uncorrected low potassium or low magnesium.
It can cause fetal harm and was toxic to the fetus in rats and rabbits at doses below the human dose. Pregnancy should be avoided during treatment. In male rats, high doses reduced sperm counts and fertility.
Legal status and use in sport
In the US, toremifene is a prescription drug. It is not named among the anabolic steroids in Schedule III (21 CFR 1308.13).
WADA lists toremifene by name under S4.2, anti-estrogenic substances, prohibited at all times in and out of competition (WADA 2026 Prohibited List). In a small anti-doping study, toremifene 120 mg/day for 2 days altered urinary testosterone, epitestosterone and androstenedione in men, but did not change the testosterone/epitestosterone ratio (Mazzarino et al., Steroids 2011).
Key takeaways
- A chlorinated tamoxifen. Toremifene is a triphenylethylene SERM approved at 60 mg/day for metastatic breast cancer in postmenopausal women; the US brand Fareston is discontinued but generics remain.
- Same efficacy as tamoxifen in breast cancer. Trials and a Cochrane review found similar response, progression and survival, and doses above 60 mg added nothing but nausea.
- QT prolongation is the signature risk. The boxed warning reflects a mean QTc rise of 26 ms at 80 mg and 65 ms at 300 mg, made worse by CYP3A4 inhibitors.
- Different metabolism from tamoxifen. CYP3A4, not CYP2D6, is the main route, and the half-life is about 5 days.
- Male data are mixed. At 80 mg/day it raised bone density and modestly cut vertebral fractures in men on ADT, but it did not prevent prostate cancer, and short-term use in healthy older men raised SHBG rather than free testosterone.
- No PCT evidence. No controlled trial has tested toremifene for gynecomastia or for recovery after anabolic steroid use, and WADA prohibits it at all times.
Sources
- Kyowa Kirin. Fareston (toremifene citrate) tablets, prescribing information. DailyMed.
- Rising Pharma. Toremifene citrate tablets, prescribing information. DailyMed.
- US Food and Drug Administration. Drugs@FDA: Fareston, NDA 020497. Drugs@FDA.
- Food and Drug Administration. Determination that protamine sulfate (protamine sulfate) intravenous; solution, 50 milligrams/5 milliliters, and other drug products were not withdrawn from sale for reasons of safety or effectiveness. Federal Register. June 8, 2026;91:34634 (FR Doc 2026-11429). Federal Register.
- National Center for Biotechnology Information. Toremifene, PubChem CID 3005573. PubChem.
- Hayes DF, Van Zyl JA, Hacking A, et al. Randomized comparison of tamoxifen and two separate doses of toremifene in postmenopausal patients with metastatic breast cancer. J Clin Oncol. 1995;13(10):2556–2566. PubMed.
- Mao C, Yang ZY, He BF, et al. Toremifene versus tamoxifen for advanced breast cancer. Cochrane Database Syst Rev. 2012;(7):CD008926. PubMed.
- Zhou WB, Ding Q, Chen L, et al. Toremifene is an effective and safe alternative to tamoxifen in adjuvant endocrine therapy for breast cancer: results of four randomized trials. Breast Cancer Res Treat. 2011;128(3):625–631. PubMed.
- Zhou W, Jiang Y, Xu Y, et al. Comparison of adverse drug reactions between tamoxifen and toremifene in breast cancer patients with different CYP2D6 genotypes: a propensity-score matched cohort study. Int J Cancer. 2022;150(10):1664–1676. PubMed.
- Roelfsema F, Yang RJ, Takahashi PY, et al. Effects of toremifene, a selective estrogen receptor modulator, on spontaneous and stimulated GH secretion, IGF-I, and IGF-binding proteins in healthy elderly subjects. J Endocr Soc. 2018;2(2):154–165. PubMed.
- Farmakiotis D, Farmakis C, Rousso D, et al. The beneficial effects of toremifene administration on the hypothalamic-pituitary-testicular axis and sperm parameters in men with idiopathic oligozoospermia. Fertil Steril. 2007;88(4):847–853. PubMed.
- Tsourdi E, Kourtis A, Farmakiotis D, et al. The effect of selective estrogen receptor modulator administration on the hypothalamic-pituitary-testicular axis in men with idiopathic oligozoospermia. Fertil Steril. 2009;91(4 Suppl):1427–1430. PubMed.
- Smith MR, Malkowicz SB, Chu F, et al. Toremifene increases bone mineral density in men receiving androgen deprivation therapy for prostate cancer: interim analysis of a multicenter phase 3 clinical study. J Urol. 2008;179(1):152–155. PubMed.
- Smith MR, Malkowicz SB, Chu F, et al. Toremifene improves lipid profiles in men receiving androgen-deprivation therapy for prostate cancer: interim analysis of a multicenter phase III study. J Clin Oncol. 2008;26(11):1824–1829. PubMed.
- Smith MR, Morton RA, Barnette KG, et al. Toremifene to reduce fracture risk in men receiving androgen deprivation therapy for prostate cancer. J Urol. 2010;184(4):1316–1321. PubMed.
- Price D, Stein B, Sieber P, et al. Toremifene for the prevention of prostate cancer in men with high grade prostatic intraepithelial neoplasia: results of a double-blind, placebo controlled, phase IIB clinical trial. J Urol. 2006;176(3):965–970. PubMed.
- Taneja SS, Morton R, Barnette G, et al. Prostate cancer diagnosis among men with isolated high-grade intraepithelial neoplasia enrolled onto a 3-year prospective phase III clinical trial of oral toremifene. J Clin Oncol. 2013;31(5):523–529. PubMed.
- Grouthier V, Lebrun-Vignes B, Glazer AM, et al. Increased long QT and torsade de pointes reporting on tamoxifen compared with aromatase inhibitors. Heart. 2018;104(22):1859–1863. PubMed.
- Mazzarino M, de la Torre X, Botrè F. Urinary excretion profiles of toremifene metabolites by liquid chromatography-mass spectrometry. Towards targeted analysis to relevant metabolites in doping control. Anal Bioanal Chem. 2011;401(2):529–541. PubMed.
- Mazzarino M, Braganò MC, de la Torre X, et al. Relevance of the selective oestrogen receptor modulators tamoxifen, toremifene and clomiphene in doping field: endogenous steroids urinary profile after multiple oral doses. Steroids. 2011;76(12):1400–1406. PubMed.
- World Anti-Doping Agency. The 2026 Prohibited List. WADA 2026 Prohibited List.
- Code of Federal Regulations. 21 CFR 1308.13, Schedule III. 21 CFR 1308.13.