How Do Antineoplastic Estrogen Receptor Antagonists Work?

Antineoplastic estrogen receptor antagonists are a class of drugs used for treating patients with estrogen sensitive breast cancers. Estrogen receptor antagonists are antineoplastic nonsteroidal hormonal agents with potent antiestrogenic properties. They bind to estrogen (a female hormone) receptors and inhibit the action of estrogen which stops the growth of certain breast tumors that need estrogen to grow and spread to other parts of the body.

Estrogen receptor antagonists are administered via the intravenous (into a vein) route.

Estrogen receptor antagonists work in the following ways:

• They belong to a class of medications known as "antiestrogens" that work by blocking the activity of estrogen in the breast tissue that may stop the growth of some breast tumors that need estrogen to grow.
• They interfere with the effects of estrogen in the breast tissue, inhibiting the growth and spread of cancer cells.

Antineoplastic estrogen receptor antagonists are used for:

• Treatment of adults with estrogen receptor-positive metastatic breast cancer
• Adjuvant treatment of adults with early-stage estrogen receptor-positive breast cancer and to reduce the occurrence of contralateral breast cancer in adults when used as adjuvant therapy for breast cancer
• Breast cancer prevention

Off-label uses include:

• Ovulation induction
• Mastalgia (breast pain)

Some of the common side effects include:

• Nausea
• Vomiting
• Hot flashes
• Leg cramps
• Muscle pain
• Constipation
• Diarrhea
• Abdominal pain
• Headache
• Tingling/numbness of the skin
• Tiredness/weakness
• Loss of appetite
• Pain, redness, swelling, hardness, or itching at the injection site

Other rare side effects include:

• Dizziness 
• Fatigue 
• Weight loss
• Hair loss
• Excessive sweating
• Anemia (low red blood cell count)
• Insomnia (trouble falling and/or staying asleep)
• Shortness of breath
• Chills, sore throat, fever, or cough
• Chest pain
• Rash/hives/itching
• Yellowing of the skin or eyes
• Dark urine
• Swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs
• Thrombocytopenia (low blood platelet count)
• Hypercalcemia (high blood calcium level)
• Amenorrhea (absence of menstruation)
• Depression
• Loss of libido 

Information contained herein is not intended to cover all possible side effects, precautions, warnings, drug interactions, allergic reactions, or adverse effects. Check with your doctor or pharmacist to make sure these drugs do not cause any harm when you take them along with other medicines. Never stop taking your medication and never change your dose or frequency without consulting your doctor

Generic and brand names of antineoplastic estrogen receptor antagonists include:

• Fareston
• Faslodex
• Fulvestrant
• Soltamox
• Tamoxifen
• Toremifene