Important: This page is general information, not medical advice. It does not recommend or prescribe any treatment. Always consult your doctor or pharmacist before starting, stopping or changing any medicine.
Quick facts
- Drug class
- Estrogen Receptor Antagonist [EPC], Estrogen Receptor Antagonists [MoA], Selective Estrogen Receptor Modulators [MoA]
- How it is given
- intramuscular
- Type
- human prescription drug
- RxNorm ID
- 727762
We do not publish dosing. How much of this medicine to take, how often, and for how long depends on your age, weight, kidney and liver function, other conditions and other medicines. That is a decision for the person who prescribes or dispenses it. Follow the directions on your own pack and ask your pharmacist if anything is unclear.
What it is used to treat
Fulvestrant Injection is an estrogen receptor antagonist indicated for the treatment of: Hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer in postmenopausal women not previously treated with endocrine therapy. ( 1 ) HR-positive advanced breast cancer in postmenopausal women with disease progression following endocrine therapy. ( 1 ) HR-positive, HER2-negative advanced or metastatic breast cancer in postmenopausal women in combination with ribociclib, as initial endocrine based therapy or following disease progression on endocrine therapy. ( 1 ) HR-positive, HER2-negative advanced or metastatic breast cancer in combination with palbociclib or abemaciclib in women with disease progression after endocrine therapy. ( 1 ) Monotherapy Fulvestrant Injection is indicated for the treatment of: Hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative advanced breast cancer in postmenopausal women not previously treated with endocrine therapy, or HR-positive advanced breast cancer in postmenopausal women with disease progression following endocrine therapy. Combination Therapy Fulvestrant Injection is indicated for the treatment of: HR-positive, HER2-negative advanced or metastatic breast cancer in postmenopausal women in combination with ribociclib as initial endocrine based therapy or following disease progression on endocrine therapy. HR-positive, HER2-negative advanced or metastatic breast cancer in combination with palbociclib or abemaciclib in women with disease progression after endocrine therapy.
About this medicine
Fulvestrant Injection for intramuscular administration is an estrogen receptor antagonist. The chemical name is 7-alpha-[9-(4,4,5,5,5-penta fluoropentylsulphinyl) nonyl]estra-1,3,5-(10)-triene-3,17-beta-diol. The molecular formula is C 32 H 47 F 5 O 3 S and its structural formula is: Fulvestrant is a white powder with a molecular weight of 606.77. The solution for injection is a clear, colorless to yellow, viscous liquid. Each injection contains as inactive ingredients: 10% w/v (12% v/v) Alcohol, USP, 10% w/v Benzyl Alcohol, NF, and 15% w/v Benzyl Benzoate, USP, as co-solvents, and made up to 100% w/v with Castor Oil, USP as a co-solvent and release rate modifier. Structural Formula
How it works
12.1 Mechanism of Action Many breast cancers have estrogen receptors (ER) and the growth of these tumors can be stimulated by estrogen. Fulvestrant is an estrogen receptor antagonist that binds to the estrogen receptor in a competitive manner with affinity comparable to that of estradiol and downregulates the ER protein in human breast cancer cells. In vitro studies demonstrated that fulvestrant is a reversible inhibitor of the growth of tamoxifen-resistant, as well as estrogen-sensitive human breast cancer (MCF-7) cell lines. In in vivo tumor studies, fulvestrant delayed the establishment of tumors from xenografts of human breast cancer MCF-7 cells in nude mice. Fulvestrant inhibited the growth of established MCF-7 xenografts and of tamoxifen-resistant breast tumor xenografts. Fulvestrant showed no agonist-type effects in in vivo uterotrophic assays in immature or ovariectomized mice and rats. In in vivo studies in immature rats and ovariectomized monkeys, fulvestrant blocked the uterotrophic action of estradiol. In postmenopausal women, the absence of changes in plasma concentrations of FSH and LH in response to fulvestrant treatment (250 mg monthly) suggests no peripheral steroidal effects.
Who should not take it
Fulvestrant Injection is contraindicated in patients with a known hypersensitivity to the drug or to any of its components. Hypersensitivity reactions, including urticaria and angioedema, have been reported in association with Fulvestrant Injection [see Adverse Reactions ( 6.2 )]. Hypersensitivity. ( 4 )
Warnings and cautions
Risk of Bleeding: Use with caution in patients with bleeding diatheses, thrombocytopenia, or anticoagulant use. ( 5.1 ) Increased Exposure in Patients with Hepatic Impairment: Use a 250 mg dose for patients with moderate hepatic impairment. ( 2.2 , 5.2 , 8.6 ) Injection Site Reaction: Use caution while administering Fulvestrant Injection at the dorsogluteal injection site due to the proximity of the underlying sciatic nerve. ( 5.3 ) Embryo-Fetal Toxicity: Can cause fetal harm. Advise females of reproductive potential of the potential risk to a fetus and to use effective contraception. ( 5.4 , 8.1 , 8.3 ) Immunoassay Measurement of Serum Estradiol: Fulvestrant Injection can interfere with estradiol measurement by immunoassay, resulting in falsely elevated estradiol levels. ( 5.5 ) 5.1 Risk of Bleeding Because Fulvestrant Injection is administered intramuscularly, it should be used with caution in patients with bleeding diatheses, thrombocytopenia, or anticoagulant use. 5.2 Increased Exposure in Patients with Hepatic Impairment The safety and pharmacokinetics of Fulvestrant Injection were evaluated in a study in seven subjects with moderate hepatic impairment (Child-Pugh class B) and seven subjects with normal hepatic function. Exposure was increased in patients with moderate hepatic impairment, therefore a dose of 250 mg is recommended [see Dosage and Administration ( 2.2 )]. Fulvestrant Injection has not been studied in patients with severe hepatic impairment (Child-Pugh class C) [see Use in Specific Populations ( 8.6 )]. 5.3 Injection Site Reaction Injection site related events including sciatica, neuralgia, neuropathic pain, and peripheral neuropathy have been reported with Fulvestrant Injection. Caution should be taken while administering Fulvestrant Injection at the dorsogluteal injection site due to the proximity of the underlying sciatic nerve [see Dosage and Administration ( 2.3 ) and Adverse Reactions ( 6.1 )] . 5.4 Embryo-Fetal Toxicity Based on findings from animal studies and its mechanism of action, Fulvestrant Injection can cause fetal harm when administered to a pregnant woman. […]
Reported side effects
The following adverse reactions are discussed in more detail in other sections of the labeling: Risk of Bleeding [see Warnings and Precautions ( 5.1 )] Increased Exposure in Patients with Hepatic Impairment [see Warnings and Precautions ( 5.2 )] Injection Site Reaction [see Warnings and Precautions ( 5.3 )] Embryo-Fetal Toxicity [see Warnings and Precautions ( 5.4 )] The most common adverse reactions occurring in ≥5% of patients receiving Fulvestrant Injection 500 mg were: injection site pain, nausea, bone pain, arthralgia, headache, back pain, fatigue, pain in extremity, hot flash, vomiting, anorexia, asthenia, musculoskeletal pain, cough, dyspnea, and constipation. ( 6.1 ) Increased hepatic enzymes (ALT, AST, ALP) occurred in >15% of Fulvestrant Injection patients and were not dose-dependent. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Meitheal Pharmaceuticals, Inc. at 1-844-824-8426 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, the adverse reaction rates observed cannot be directly compared to rates in other trials and may not reflect the rates observed in clinical practice. Monotherapy Comparison of Fulvestrant Injection 500 mg and Fulvestrant Injection 250 mg (CONFIRM) The following adverse reactions (ARs) were calculated based on the safety analysis of CONFIRM comparing the administration of Fulvestrant Injection 500 mg intramuscularly once a month with Fulvestrant Injection 250 mg intramuscularly once a month. The most frequently reported adverse reactions in the Fulvestrant Injection 500 mg group were injection site pain (11.6% of patients), nausea (9.7% of patients), and bone pain (9.4% of patients); the most frequently reported adverse reactions in the Fulvestrant Injection 250 mg group were nausea (13.6% of patients), back pain (10.7% of patients), and injection site pain (9.1% of patients). Table 1 lists adverse reactions reported with an incidence of 5% or greater, regardless of assessed causality, from CONFIRM. […]
Interactions with other medicines
There are no known drug-drug interactions. Although, fulvestrant is metabolized by CYP 3A4 in vitro , drug interactions studies with ketoconazole or rifampin did not alter fulvestrant pharmacokinetics. Dose adjustment is not needed in patients co-prescribed CYP 3A4 inhibitors or inducers [see Clinical Pharmacology ( 12.3 )] . There are no known drug-drug interactions. ( 7 )
Use in specific groups
Lactation: Advise not to breastfeed. ( 8.2 ) 8.1 Pregnancy Risk Summary Based on findings from animal studies and its mechanism of action, Fulvestrant Injection can cause fetal harm when administered to a pregnant woman [see Clinical Pharmacology ( 12.1 )]. There are no available data in pregnant women to inform the drug-associated risk. In animal reproduction studies, administration of fulvestrant to pregnant rats and rabbits during organogenesis caused embryo-fetal toxicity, including skeletal malformations and fetal loss, at daily doses that were 6% and 30% of the maximum recommended human dose based on mg/m 2 , respectively [see Data ] . Advise pregnant women of the potential risk to a fetus. The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2-4% and 15-20%, respectively. Data Animal Data Administration of fulvestrant to rats prior to and up to implantation caused embryonic loss at daily doses that were 0.6% of the daily maximum recommended human dose based on mg/m 2 . When fulvestrant was administered to pregnant rats during the period of organogenesis, intramuscular doses ≥0.1 mg/kg/day (6% of the human recommended dose based on mg/m 2 ) caused effects on embryo-fetal development consistent with its antiestrogenic activity. Fulvestrant caused an increased incidence of fetal abnormalities in rats (tarsal flexure of the hind paw at 2 mg/kg/day; equivalent to the human dose based on mg/m 2 ) and non-ossification of the odontoid and ventral tubercle of the first cervical vertebra at doses ≥0.1 mg/kg/day. Fulvestrant administered at 2 mg/kg/day caused fetal loss. When administered to pregnant rabbits during the period of organogenesis, fulvestrant caused pregnancy loss at an intramuscular dose of 1 mg/kg/day (equivalent to the human dose based on mg/m 2 ). Further, at 0.25 mg/kg/day (30% the human dose based on mg/m 2 ), fulvestrant caused increases in placental weight and post-implantation loss in rabbits. […]
If too much is taken
Human experience of overdose with Fulvestrant Injection is limited. There are isolated reports of overdose with Fulvestrant Injection in humans. No adverse reactions were seen in healthy male and female volunteers who received intravenous fulvestrant, which resulted in peak plasma concentrations at the end of the infusion, that were approximately 10 to 15 times those seen after intramuscular injection. The potential toxicity of fulvestrant at these or higher concentrations in cancer patients who may have additional comorbidities is unknown. There is no specific treatment in the event of fulvestrant overdose, and symptoms of overdose are not established. In the event of an overdose, healthcare practitioners should follow general supportive measures and should treat symptomatically.
Storing it safely
Storage REFRIGERATE, 2° to 8°C (36° to 46°F). TO PROTECT FROM LIGHT, STORE IN THE ORIGINAL CARTON UNTIL TIME OF USE. Sterile, Nonpyrogenic, PVC-free, DEHP-free.
Before you take anything new
Tell your pharmacist or doctor about every medicine you take — including ones bought without a prescription, herbal products and supplements. Interactions are one of the most common avoidable causes of harm from medicines, and a pharmacist can check your full list in a couple of minutes.
This page is built from the openFDA record of the U.S. Food and Drug Administration's approved labelling for this product, effective 17 June 2024. Label text has been shortened and reformatted for readability; safety wording has not been altered in meaning. FDA labelling describes products approved in the United States — brand names, strengths, formulations and approved uses may differ in your country. Always read the leaflet that comes with your own pack. PocketsInfo is not affiliated with, and is not endorsed by, the FDA. Retrieved 2026-07-30.