Fulvestrant

Use of Fulvestrant

Fulvestrant is a hormone therapy you may be prescribed if you have certain types of breast cancer. Fulvestrant is an estrogen receptor antagonist that binds to estrogen receptors in breast cancer cells. The hormone estrogen encourages breast cancer cells to grow, and fulvestrant works by binding and blocking the estrogen receptor, which slows the growth of cancer.

It is approved to be used for certain types of breast cancer in women, so your doctor will only prescribe it for you if it has been shown to be effective for your type of cancer.

It is given as an injection into your buttock muscle once a month, but your dose may change depending on how well it is working for you and if you are having side effects. You may also be given other medicines with fulvestrant to treat your breast cancer.

Precautions and Warnings

Before using this medication, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients (such as benzyl alcohol), which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: liver disease, bleeding problems, low platelet counts (thrombocytopenia).

This drug may make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using fulvestrant. Fulvestrant may harm an unborn baby. Your doctor should order a pregnancy test within 7 days of starting this medication. Ask about reliable forms of non-hormonal birth control (such as condoms, diaphragm with spermicide) while using this medication and for 1 year after the last dose. If you become pregnant, talk to your doctor right away about the risks and benefits of this medication.

It is unknown if this drug passes into breast milk. Because of the possible risk to the infant, breastfeeding is not recommended while using this drug and for 1 year after the last dose. Consult your doctor before breastfeeding.

Dosage

Fulvestrant is available in a pre-filled syringe of 250 mg per 5 mL.

For advanced, hormone receptor-positive breast cancer or hormone receptor-positive HER2-negative breast cancer: 500 mg IM, administered as two 5 mL injections, one in each buttock on days 1, 15, and 29, and subsequently once monthly.

For advanced or metastatic disease: Same dosing as above, in combination with ribociclib. If giving with palbociclib or ademaciclib, administer with an LHRH agonist in pre or perimenopausal patients.

In cases of moderate liver impairment, the recommendation is to reduce the dose to 250 mg.

Side Effects

Common side effects:

• injection site pain
• nausea
• muscle, joint, and bone pain
• headache
• back pain
• tiredness
• pain in arms, hands, legs, or feet
• hot flashes
• vomiting
• loss of appetite
• weakness
• cough
• shortness of breath
• constipation
• increased liver enzymes
• diarrhea