Fulvestrant
Say it: ful-VES-trant · Brand names: Faslodex
Fulvestrant is a hormone therapy shot that blocks and breaks down the estrogen receptor in breast cancer cells.
What it is
Many breast cancers use the hormone estrogen to grow. Fulvestrant attaches to the estrogen receptor on cancer cells and helps the body break it down. Without the receptor, estrogen cannot tell the cancer to grow.
Often used for
- hormone receptor positive breast cancer after menopause that is advanced or has spread
- given alone or with targeted pills such as palbociclib, ribociclib, abemaciclib, alpelisib, or capivasertib
How you get it
Fulvestrant is given in the clinic as 2 shots, one into the muscle of each buttock. Each shot takes 1 to 2 minutes. It is usually given every 2 weeks for the first 3 doses, then once a month. Your schedule may be different.
Common side effects and what helps
- Pain, soreness, or a lump where the shot was given. A warm compress may help. Tell your team if it lasts.
- Feeling sick to your stomach or throwing up. Eat small meals and ask your team about anti-nausea medicine.
- Joint or muscle aches and stiffness. Regular gentle exercise often helps.
- Hot flashes or night sweats. Dress in layers, keep your room cool, and limit caffeine and alcohol.
- Feeling tired or weak. Rest when you need to, and try short walks.
- Headache. Ask your team which pain medicines are safe.
- Changes in liver blood tests. Your team will check these.
- Constipation. Drink fluids and eat fiber.
Call your care team right away if you have
- Pain, numbness, tingling, or weakness that spreads down your leg after a shot
- Bleeding or a large bruise at the shot site
- Swelling of your face or throat, hives, or trouble breathing
- Swelling, pain, or warmth in one leg, or sudden shortness of breath
- Yellow skin or eyes, dark tea colored urine, or pain on the right side of your belly
Before you start, tell your team
- If you are pregnant, may become pregnant, or are breastfeeding
- If you have bleeding problems or take a blood thinner
- If you have low platelets
- If you have liver problems
- All the medicines, vitamins, and herbal products you take, since some can change how this medicine works
Good to know
- Because it is given into the muscle, there is a higher chance of bleeding or bruising if you have low platelets or take a blood thinner.
- The shots are given near a large nerve. Tell your team about any leg pain or numbness afterward.
- It can make some estrogen blood tests read falsely high.
- This medicine can harm an unborn baby. Use birth control during treatment and for some time after. Ask your team how long.
Questions to ask
- How often will I get this medicine?
- What can I do for soreness after the shots?
- How will we know if this medicine is working?
- Which side effects should I call about right away, and which can wait until my next visit?
Side effect guides
Sources
Quick answers
- What is Fulvestrant?
- Fulvestrant is a hormone therapy shot that blocks and breaks down the estrogen receptor in breast cancer cells. Brand names: Faslodex.
- What is Fulvestrant used for?
- hormone receptor positive breast cancer after menopause that is advanced or has spread; given alone or with targeted pills such as palbociclib, ribociclib, abemaciclib, alpelisib, or capivasertib.
- How is Fulvestrant given?
- Fulvestrant is given in the clinic as 2 shots, one into the muscle of each buttock. Each shot takes 1 to 2 minutes. It is usually given every 2 weeks for the first 3 doses, then once a month. Your schedule may be different.
- What are the common side effects of Fulvestrant?
- Pain, soreness, or a lump where the shot was given. Feeling sick to your stomach or throwing up. Joint or muscle aches and stiffness. Hot flashes or night sweats. Feeling tired or weak. Headache. Changes in liver blood tests. Constipation.
- When should I call my care team while taking Fulvestrant?
- Pain, numbness, tingling, or weakness that spreads down your leg after a shot; Bleeding or a large bruise at the shot site; Swelling of your face or throat, hives, or trouble breathing; Swelling, pain, or warmth in one leg, or sudden shortness of breath; Yellow skin or eyes, dark tea colored urine, or pain on the right side of your belly.
Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.