Fulvestrant (Faslodex)

At a glance

Fulvestrant is a medicine used in specialist cancer care. Brand names include Faslodex. The practical instructions depend on the exact prescription and product supplied.

Your prescription and the instructions for your own product take priority over a general guide. Keep the medicine leaflet as well as your treatment plan, especially if the brand or formulation changes.

You do not need to remember every possible side effect. Start with the administration instructions and the section on urgent help. Most people experience only some of the effects described here. Tell your team about difficulties early: supportive treatment, a planned pause or a different medicine may make treatment easier to continue.

How it works

Fulvestrant is an oestrogen-receptor degrader, or SERD. It blocks receptor signalling and reduces the amount of receptor available in sensitive cancer cells. It is given into muscle, rather than taken as a daily tablet.

Is this treatment suitable for me?

Your team considers hormone-receptor findings, menopausal status and the wider treatment plan. Fulvestrant may be used with a targeted medicine. If ovarian function remains active, ovarian suppression may also be required; fulvestrant injections do not replace that separate treatment.

Your oncologist considers the biology of the cancer, treatments already received, other illnesses and your preferences. The aim may be to reduce the chance of cancer returning, control cancer that is present, or relieve symptoms. Ask which aim applies to you and how benefit will be assessed. The same medicine can be used for different lengths of time in different treatment plans.

A brand name alone does not tell you whether a medicine is suitable. The dose, formulation and other medicines in the plan also matter. Discuss the possible benefits and risks with your care team.

Before treatment

Mention bleeding disorders, low platelets, anticoagulants, liver disease and previous buttock or sciatic-nerve problems. If pregnancy is possible, a pregnancy test is needed before treatment; the US label specifies within the preceding seven days. Ensure the team has explained all partner medicines because many combination side effects come from those drugs.

Bring an up-to-date list of prescription medicines, pharmacy medicines, supplements and traditional or herbal remedies. Include medicines used only occasionally, creams containing hormones, and anything recently stopped. Mention previous allergies and describe what happened, rather than only naming the drug. Your pharmacist can check the whole list together.

Tell the team about any planned operation, dental procedure, travel or difficulty attending appointments. Discuss costs and supply before the first dose if obtaining regular refills may be difficult. Agree who will arrange repeat prescriptions and tests. Keep your own hospital's daytime and out-of-hours contact details where you and a caregiver can find them quickly.

How to take or receive treatment

The usual dose is 500 mg as two slow intramuscular injections, one into each buttock. The initial schedule is days 1, 15 and 29, followed by monthly doses. The extra early injection helps establish treatment exposure. Moderate liver impairment can require a lower prescribed dose.

A healthcare professional gives the injections. Tell the nurse immediately if you feel sharp radiating pain, numbness or weakness during administration. If an appointment is missed, contact the clinic promptly for a revised date; do not assume the early loading appointment is optional.

Check the date of the next appointment before leaving the clinic. An injection described as monthly may have a specific number of weeks or calendar-month interval; use the date your team gives you. Contact the clinic promptly if an appointment is missed or needs changing. Do not arrange an extra dose, substitute another depot strength or change the interval yourself.

Tell the nurse about blood thinners, unusual bruising, an infection near the planned injection site or a previous injection reaction. The preparation and route are specific to the product. Fulvestrant injections are given by a healthcare professional.

The clinic usually stores and prepares fulvestrant. Faslodex needs refrigeration at 2–8°C (36–46°F) and protection from light in its original carton. If you need to collect or transport it, ask the pharmacy for a suitable transport plan and instructions for your exact product. Do not give yourself these injections.

Use a calendar or a phone reminder that records what was actually taken or given. A tick made after a dose is more useful than one made in advance. If someone helps with medicines, agree who records each dose so it is not accidentally repeated. Keep the drug name, strength and current instructions together; an old prescription may no longer describe your current dose.

Contact the treating team if a supply problem or illness is likely to interrupt treatment. Do not stretch the supply by taking smaller doses or lengthening intervals yourself. If you receive too much medicine, seek urgent advice and have the packaging and dose times available. Do not induce vomiting.

Monitoring your treatment

Reviews assess response, symptoms, liver function and injection tolerance. Partner treatments may require additional blood counts, glucose tests, ECGs or other checks. Fulvestrant can interfere with some oestradiol immunoassays and produce a falsely high result; laboratories need to know you receive it.

Monitoring has two purposes: checking whether treatment is helping and detecting problems that may be silent at first. Your schedule depends on the medicine, any partner treatment and your general health. Ask which results need to be reviewed before the next prescription or injection, and who will contact you if a result is abnormal.

Record symptoms that affect eating, walking, sleep or daily activities, along with when they began. Bring this record to appointments. A single symptom or blood result rarely explains the whole picture; the team may compare trends, examination findings and scans. Feeling well is welcome, but it does not remove the need for planned monitoring.

Common side effects

Effects to discuss with your team

Injection-site soreness, fatigue, nausea, hot flushes and muscle or joint pain can occur. Mild soreness should improve, but worsening pain, marked swelling or a persistent difficulty walking needs review. Mention symptoms rather than changing your next appointment yourself.

Fulvestrant and ovarian-suppression injections have different jobs. Fulvestrant acts at the oestrogen receptor; a GnRH injection suppresses hormone production by the ovaries. If both are prescribed, each has its own schedule. Keep their names and dates separate on your calendar to prevent one appointment being mistaken for the other.

Combination treatment also needs a clear treatment plan. A targeted partner may be taken daily, on selected days or in cycles and may require different blood tests. Ask which medicine to hold if a particular side effect occurs; do not assume an instruction to pause tablets also means cancelling fulvestrant.

Injection comfort matters. Tell the nurse about previous severe pain, scar tissue, blood thinners or difficulty lying or standing in the required position. Mild soreness can occur, but worsening symptoms or pain extending down the leg should not be dismissed. Ask which simple pain-relief measure is suitable for your health and medicines.

Fulvestrant can make certain oestradiol blood tests misleading because its structure resembles the hormone. A result needs laboratory interpretation before it is used to judge ovarian suppression. Keep the medicine name on every test request and tell clinicians outside oncology that you receive it. This issue does not mean all hormone tests are unusable; an appropriate method can help resolve it.

Making symptoms easier to manage

Tell the team which symptom is causing the most difficulty. Describe its effect on ordinary tasks: for example, whether pain prevents dressing or tiredness stops you preparing food. This helps the team choose practical support and judge whether treatment needs adjustment. Avoid waiting until the next routine visit if symptoms are worsening.

For mild nausea, try smaller meals and regular sips of fluid, following any food rule for the medicine. Ask about an anti-sickness medicine if needed. Repeated vomiting, inability to keep fluids down or very little urine needs prompt advice. If you have been told to restrict fluids for another illness, use that plan rather than forcing extra drinks.

Energy and emotional wellbeing

Pace demanding activities and allow rest, but keep some gentle movement in your day if you can. Persistent exhaustion deserves assessment; poor sleep, anaemia, low mood and other illnesses may contribute. Tell the team about persistent anxiety, sadness or loss of interest. If you feel at risk of harming yourself, seek emergency help and ask someone to stay with you.

Important side effects

The effects below are important because they may require tests or a change in treatment. They are not a prediction that you will develop them. New symptoms can also come from the cancer or an unrelated illness. Reporting them promptly allows the team to work out the cause; do not assume that everything is a routine treatment effect.

Bleeding or a haematoma can occur at the injection site, particularly with low platelets or anticoagulants. Sciatic nerve injury or irritation may cause radiating pain, weakness or numbness. Liver problems and serious allergic reactions are other important concerns.

Other medicines and vaccinations

There are fewer established metabolic interactions than with many oral endocrine medicines, but blood thinners increase injection-related bleeding concerns. Do not stop them yourself. Tell anyone ordering oestradiol tests about fulvestrant so an appropriate assay can be chosen. Partner medicines need their own interaction review.

Ask the oncology pharmacist to check new medicines before you start them, including antibiotics prescribed elsewhere. Do not stop essential treatment for another illness on your own. If an interaction is possible, the prescribers can choose an alternative, adjust a dose or arrange monitoring. Herbal products labelled natural can still alter drug levels or have hormone-like effects.

Vaccination advice depends on your complete treatment plan. Hormone treatment alone does not automatically mean that every vaccine is unsuitable. Ask about influenza, COVID-19 and other recommended vaccines; live vaccines need a specific check if you also receive chemotherapy, an immune-suppressing medicine or certain doses of steroid. Tell the vaccination service all the treatments you receive.

Everyday life

Food and movement

Aim for regular meals with enough protein and a varied range of foods that you can tolerate. Tell the team about unplanned weight loss, rapid weight gain or difficulty eating. A dietitian can adapt advice to diabetes, kidney problems, bowel symptoms or a restricted appetite. Do not start a restrictive diet or high-dose supplement as a substitute for treatment.

Choose activity that suits your strength and balance. Short walks or gentle exercises may be easier to sustain than occasional strenuous sessions. If cancer affects your bones, or you have osteoporosis, ask which movements and resistance exercises are safe before starting a new programme. New focal bone pain should be assessed rather than exercised through.

Work and travel

Many people continue some usual activities, but flexibility helps while you learn how treatment affects you. Discuss rest breaks, shorter hours or help with physically demanding work if needed. Avoid driving or operating machinery when dizzy, sleepy, confused or affected by visual symptoms. Follow any additional driving advice after a seizure or loss of consciousness.

Plan travel around prescriptions, injections and tests. Carry an up-to-date medicine list and enough supply for the agreed trip, with advice about storage and time-zone changes. For long journeys, discuss mobility and your individual clot risk. Do not start aspirin or a blood thinner simply because you are travelling.

Relationships and support

Changes in energy, body image or sexual function can affect relationships. You can ask for help privately, with or without a partner present. There may be practical measures or specialist support for discomfort and intimacy. A caregiver can help record symptoms and organise appointments while leaving treatment decisions and personal information under your control.

Fertility, pregnancy and breastfeeding

The US label advises effective contraception during treatment and for one year after the final dose, and no breastfeeding during treatment or for one year afterwards. Ask for a suitable non-hormonal plan and account for other drugs in the regimen. Fertility may be affected.

Tell the team before treatment if having children in the future matters to you. Fertility preservation needs discussion before exposure where possible. Reduced fertility is not the same as reliable contraception, and an absence of periods or reduced sexual function does not prove that pregnancy is impossible.

Ask your team which contraception to use and how long to continue it, taking account of every medicine in your regimen. A partner drug may require a longer precaution period than this medicine alone. If pregnancy is suspected in you or a partner during a risk period, contact the treating team promptly for individual advice. Do not make pregnancy or breastfeeding decisions from a generic time interval without checking your own treatment plan.

After treatment

Fulvestrant remains in the body for a prolonged period after injections stop. Keep the last injection date available for future clinicians, pregnancy planning and interpretation of hormone tests. Confirm which partner medicines and monitoring continue.

Before a planned stop, confirm which medicines end, which continue, and when the next review is due. Return unused medicine through the pharmacy's recommended route; do not give it to another person. Keep a record of the last dose and any side effects that still need follow-up.

Changes caused by treatment may settle gradually, and some need ongoing support. Report persistent symptoms or new problems after treatment rather than assuming they will disappear on their own. Continue the agreed follow-up and screening plan. If treatment is being changed, ask your team to help you update your treatment schedule so that old and new instructions are not accidentally combined.

Common questions