Description

Faslodex (fulvestrant) is an anti-estrogen medication used to treat certain types of hormone receptor-positive, advanced breast cancer in postmenopausal women.The key points are:

• Faslodex is indicated as monotherapy for the treatment of estrogen receptor positive, locally advanced or metastatic breast cancer in postmenopausal women:
  • Not previously treated with endocrine therapy, or
  • With disease relapse on or after adjuvant antioestrogen therapy, or disease progression on antioestrogen therapy 
• The recommended dose is 500 mg administered intramuscularly as two 5 mL injections, one in each buttock, on days 1, 15, 29 and once monthly thereafter .
• Faslodex 250 mg/5 mL is supplied as a single-dose prefilled syringe. The 250 mg dose was found to be at least as effective as 1 mg daily anastrozole, with similar safety and efficacy profiles .
• Common side effects include injection site pain, headache, back pain, fatigue, nausea, vomiting, bone pain, and arthralgia .
• Faslodex is not recommended for use in children, and no dose adjustments are required for patients with renal or hepatic impairmen
  

  Mechanism of Action

  Faslodex is a selective estrogen receptor downregulator (SERD). It binds to the estrogen receptor with affinity comparable to that of estradiol, blocks the binding of estradiol, and downregulates the estrogen receptor protein in human breast cancer cells.

  Lack of Agonist Effects

  Unlike tamoxifen, which has both estrogen agonist and antagonist effects, Faslodex has no known agonist effects. It is a pure estrogen antagonist in breast tissue.

  Intramuscular Administration

  Faslodex is administered as an intramuscular injection, rather than orally like many other breast cancer medications. This allows for a more direct delivery of the drug.

  Dose Comparison

  The 250 mg dose was found to be at least as effective as 1 mg daily anastrozole, with similar safety and efficacy profiles. This suggests the 250 mg dose is an effective and well-tolerated regimen.

  Lack of Metabolites

  Faslodex is not extensively metabolized. The parent compound is the major circulating component in the plasma after intramuscular administration. This may help simplify the pharmacokinetics compared to drugs that generate many metabolites.

  Indication

  Faslodex is indicated for the treatment of hormone receptor-positive advanced breast cancer in postmenopausal women. It is one of the few injectable medications approved for this indication.

  Key Benefits

  • Effective at prolonging the time patients with estrogen receptor-positive, locally advanced or metastatic breast cancer can live without their disease getting worse 
  • As effective as the aromatase inhibitor anastrozole in terms of progression-free survival, objective response, and time to death 
  • Effective in combination with palbociclib in patients with HR-positive, HER2-negative advanced or metastatic breast cancer 
  • Blocks the estrogen receptor and causes a decrease in the number of estrogen receptors, slowing tumor cell growth 

  Key Ingredients

  • Fulvestrant – the active pharmaceutical ingredient, an anti-estrogen that binds to and degrades the estrogen receptor 
  • Ethanol (96%, 500 mg) – a solvent used in the formulation 
  • Benzyl alcohol (500 mg) – a preservative                                                                          Benzyl benzoate (750 mg) – a solvent used in the formulation                                              key precautions to take when using Faslodex (fulvestrant):
    

    Bleeding Disorders

    Faslodex should be used with caution in patients with bleeding disorders, decreased platelet count, or who are receiving anticoagulant medications. The intramuscular route of administration poses a risk of bleeding complications in these patients .

    Hepatic Impairment

    Patients with moderate hepatic impairment (Child-Pugh class B) should receive a reduced dose of 250 mg of Faslodex. The safety and pharmacokinetics have not been fully evaluated in patients with severe hepatic impairment (Child-Pugh class C) .

    Pregnancy and Breastfeeding

    Faslodex can harm an unborn baby. Women of childbearing potential should use effective contraception during treatment and for at least 1 year after the last dose. Breastfeeding is not recommended during treatment and for at least 1 year after the last dose .

    Allergic Reactions

    Patients should be monitored for signs of allergic reactions, including rash, itching, swelling of the face, lips, tongue or throat, and trouble breathing. Faslodex is contraindicated in patients with a known hypersensitivity to the drug or its components .

    Injection Site Reactions

    Injection site reactions, including pain, inflammation, and nerve-related symptoms, have been reported. Caution should be taken when administering Faslodex at the dorsogluteal injection site due to the proximity of the sciatic nerves                                                   key points about the mechanism of action of Faslodex (fulvestrant) are:

    • Faslodex is an estrogen receptor (ER) antagonist. Many breast cancers have estrogen receptors and their growth can be stimulated by estrogen.
    • Fulvestrant, the active ingredient in Faslodex, binds to the estrogen receptor in a competitive manner with affinity comparable to that of estradiol.
    • Fulvestrant downregulates the ER protein in human breast cancer cells, thereby blocking the effects of estrogen and slowing tumor cell growth.
    • Unlike some other anti-estrogen drugs like tamoxifen, Faslodex has no known agonist (stimulatory) effects on the estrogen receptor. It is a pure estrogen antagonist in breast tissue
    Fulvestrant

    Antiestrogen medication for breast cancer

    More
    Usage

    Treats HR-positive metastatic breast cancer in postmenopausal women

    First Approval

    Approved for medical use in the United States in 2002

    Mechanism of Action

    Binds to estrogen receptor and causes protein degradation

    Dosage

    • 500 mg administered as two 5 mL intramuscular injections on days 1, 15, 29 and monthly thereafter
    • 250 mg single 5 mL injection for patients with moderate hepatic impairment

    Storage

    • Store refrigerated at 2-8°C (36-46°F) in original carton to protect from light

    Reviews

    • In clinical trials, the 250 mg dose of Faslodex was found to be at least as effective as 1 mg daily anastrozole, with similar safety and efficacy profiles .
    • Faslodex in combination with palbociclib demonstrated improved progression-free survival compared to Faslodex alone in patients with hormone receptor-positive, HER2-negative advanced breast cancer .
    • Common side effects include injection site pain, headache, back pain, fatigue, nausea, vomiting, bone pain, and arthralgia .