All About Fulvestrant

Fulvestrant is a hormone therapy drug for cancer. It is marketed as Faslodex and Fulvant among others. The medicine is indicated for the treatment of metastatic breast cancer in postmenopausal women. It is available in the form of pre-filled syringes with a strength of 250 mg/5ml.


FDA Approval History:

For Tamoxifen-Resistant Breast Cancer: Apr 25, 2002

For Advanced HR+ Breast Cancer in Postmenopausal Women: Sep 13, 2010

For HR+, HER2- Advanced Breast Cancer: Aug 28, 2017

For Advanced Breast Cancer in Combination with Abemaciclib: Nov 15, 2017


Fulvestrant is an estrogen receptor antagonist that works by binding to estrogen receptors in the tumor cells. The medicine is prescribed for the treatment of patients with:

  • Monotherapy
    • Advanced breast cancer tumors that are hormone receptor-positive and human epidermal growth factor receptor 2-negative in postmenopausal females.
    • Advanced tumors in the breast that are hormone receptor-positive and have progressed after endocrine therapy in postmenopausal females.
  • Combination therapy
    • Metastatic breast cancer tumors that are human epidermal growth factor receptor 2-negative and hormone receptor-positive with RIBOCICLIB after disease progression.
    • Metastatic tumors in the breast that are human epidermal growth factor receptor 2-negative and hormone receptor-positive with ABEMACICLIB or PALBOCICLIB after endocrine treatment.


Since fulvestrant is an estrogen receptor antagonist, it downregulates the essential proteins in the tumor. In medical terms, proteins that help in cell proliferation are known as estrogen receptors.



Estrogen Receptors: These are a group of proteins that are activated by the hormone estrogen inside the cells. They connect with estrogen to send signals that can lead to the growth of cancer.



Fulvestrant Enters: Fulvestrant connects with the estrogen receptor and reduces its ability to connect with estrogen. This way it works on the estrogen receptor instead of estrogen.



Growth Inhibition: By stopping the estrogen receptor from participating in the process of cell division, it inhibits the growth of breast cancer cell lines.

Side Effects

Mostly, oncologists prescribe over-the-counter drugs to manage the medicine’s side effects. This is why the majority of patients don’t experience any major reactions. As per the post-marketing reviews, the following are some adverse effects of fulvestrant injection.


Common side effects

  • Chills
  • Difficulty in breathing
  • Cough
  • Rapid weight gain
  • Cloudy urine
  • Pale skin
  • Fainting
  • Sore throat
  • Unusual bleeding
  • Blood in the urine


Rare side effects

  • Skin rash
  • Fast heartbeat
  • Vision changes
  • Stomach cramps
  • Light-colored stools
  • Dark urine
  • Severe headache
  • Yellowing of eyes

Warnings & Precautions

  • Pregnancy
    As per the trials in animals, Fulvestrant may result in fetal harm to the unborn baby. This is why females with childbearing potential are advised to avoid pregnancy. The doctor may also counsel about the use of effective contraceptives.
  • Breastfeeding
    Experts aren’t sure about the secretion of fulvestrant in breast milk. Thus, it is advisable to discontinue breastfeeding while you are on this hormone therapy.
  • Blood Disorders
    Administer fulvestrant with caution in patients with blood disorders like thrombocytopenia, bleeding diathesis, and anticoagulant use. This is because the drug is injected intramuscularly.
  • Hepatic Impairment
    Patients with mild to moderate hepatic impairment were studied in the clinical trials. Experts recommend a dose of 250mg. No studies were conducted to evaluate the safety of fulvestrant in severe hepatic impairment.


Before prescribing the drug, the oncologist may ask about the medicines you take & diseases you are suffering from. This information helps keep the interactions at bay.


Interaction with medicines: There is only one drug namely omacetaxine that is expected to interact with fulvestrant injection. Though more research is required to affirm the statement.


Interaction with diseases: Some diseases may affect the working of the drug. For the same reason, the oncologist asks for the patient’s medical history. Fulvestrant may not be indicated or need dose adjustments in these cases:

  • Hepatic dysfunction
  • Severe bleeding


Interaction with food and alcohol: Drinking alcohol in small amounts may not affect the functioning of the drug. Though it is advisable to avoid such drinks to be on the safer side. Interaction of fulvestrant injection with food is unknown.


The recommended dose of this drug is 500 mg. Fulvestrant injection is injected intramuscularly (into a muscle). A doctor administers two 5 mL injections into the gluteal area (buttocks) for an interval of about 2 minutes per injection. Experts recommend dose modifications in the case of patients with serious hepatic impairment.

There is no clinical evidence to determine the exact strength of overdose in humans. In case of an overdose, side effects like difficulty in breathing, chest pain, and fainting. Treatment of this condition, however, involves general supportive care only.



NOTE: This information is not an alternative to any medical prescription or advice by your doctor. Taking/selling fulvestrant injections without a prescription remains unacceptable.