Flutamide is a hormonal therapy drug used to treat prostate cancer. It’s best to read this with our general information about prostate cancer.

You have flutamide as tablets. Your cancer doctor or nurse will tell you how long you take it for.

Like all hormonal therapy drugs, flutamide can cause side effects. Some of these can be serious so it’s important to read the detailed information below. How hormonal therapy affects people varies from person to person. Your doctor or nurse can talk to you more about this and give you advice on how to manage side effects.

Tell your doctor or nurse straight away if you feel unwell or have severe side effects, including any we don’t mention here. If you need to see a health professional for any reason other than cancer, always tell them that you are having this treatment.

How flutamide works

Hormones are substances produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs. Hormonal therapies such as flutamide interfere with the way hormones are made or how they work in the body.

Most prostate cancers need the hormone testosterone to grow. Almost all testosterone in men is made by the testicles. A very small amount is made by the adrenal glands, which sit above the kidneys.

Flutamide blocks testosterone from reaching the cancer cells. Without testosterone, the prostate cancer may shrink or stop growing.

When flutamide is given

You may have flutamide for a few weeks when you first start having treatment with other hormonal therapies. These are called luteinising hormone (LH) blockers, for example goserelin (Zoladex®) and leuprorelin (Prostap®). These drugs cause a short-term rise in testosterone. This makes some symptoms, such as bone pain or problems passing urine, worse before they get better. Doctors call this tumour flare. Flutamide helps prevent this happening.

Flutamide is also used to treat prostate cancer that has spread to other parts of your body (advanced or metastatic prostate cancer). It can be given on its own or with other hormonal treatments.

Your doctor or nurse will explain why you are having flutamide and how long you will have it for.

Taking your flutamide tablets

Flutamide is taken as a tablet, three times a day. Take the tablets after meals and swallow them whole with a glass of water. Always take your tablets exactly as your nurse or pharmacist explained. This is important to make sure they work as well as possible for you.

Don’t stop taking any of your tablets unless your doctor tells you to. Here are some important things to remember:

  • If you forget to take your tablet, just take your next dose at the usual time. Don’t take a double dose.
  • Keep tablets in the original package at room temperature, and away from heat and direct sunlight.
  • Keep them safe and out of the sight and reach of children.
  • Get a new prescription before you run out of tablets and make sure you have plenty for holidays.
  • Return any remaining tablets to the pharmacist if your treatment is stopped.

Possible side effects of flutamide

We explain the most common side effects of flutamide here. We also include some rarer side effects. You may get some of the side effects we mention, but you are very unlikely to get all of them. If you are having other drugs as well, you may have some side effects that we don’t list here.

You will see a doctor or nurse regularly while you have this treatment so they can monitor its effects. Always tell your cancer doctor or nurse about the side effects you have. They can prescribe drugs to help control them and give you advice about managing them. Don’t stop taking flutamide without talking to your doctor first.

More information about this drug

We’re not able to list every side effect for this treatment here, particularly the rarer ones. For more detailed information you can visit the Medicines and Healthcare products Regulation Agency (MHRA).

Allergic reaction

Rarely, flutamide may cause an allergic reaction. Signs of a reaction can include a rash, feeling itchy, flushed or short of breath, swelling of your face or lips, or feeling dizzy or unwell. Contact your doctor straight away if you have any of these symptoms.

Breast swelling or tenderness

Many men notice slight breast swelling and tenderness. This is known as gynaecomastia. You may also notice a small amount of liquid leaking from your nipples. Your doctor can talk to you about how this can be prevented or treated.


Flutamide can cause diarrhoea. Drink plenty of fluids, at least two litres a day (three and half pints) if you have diarrhoea.

Your doctor can prescribe anti-diarrhoea tablets if needed.

Feeling sick

This is a common side effect. Your doctor can prescribe anti-sickness drugs if needed.

Sexual effects

Most men lose their sex drive and have erection difficulties (ED) during hormonal therapy. These can return to normal after you stop taking the drug but some men continue to have difficulties after treatment is over. Your doctor can prescribe treatments to help with erection difficulties, but these don’t affect sex drive.

If you need support coping with sexual difficulties, your nurse or doctor can give you information and refer you for specialist support services.

Hot flushes and sweats

These are common and can be mild or more severe. During a hot flush you feel warmth in your neck and face, and your skin may redden. Mild flushes last for a few seconds up to about a couple of minutes. More severe flushes can last for 10 minutes or more. You may have sweats and then feel cold and clammy. Some people feel anxious or irritable during a hot flush.

There are things you can do to try to reduce flushes, such as cutting down on nicotine, alcohol and hot drinks that contain caffeine such as tea and coffee.

If hot flushes are troublesome your doctor can prescribe drugs to help reduce them.

Hot flushes and sweats may get less as your body adjusts to hormonal treatment. They usually stop completely a few months after treatment finishes.

Tiredness and difficulty sleeping

Tiredness is a common side effect. Flutamide may also cause problems with falling or staying asleep. Your doctor or specialist nurse may be able to give you some help and advice with these side effects.

Exercising and doing resistance training, such as lifting weights, at least twice a week can reduce tiredness in men on hormonal therapy. It’s important to get medical advice before starting exercise. Ask your doctor or nurse what it’s safe for you to do.

You shouldn’t drive or operate machinery if you feel drowsy.

Liver changes

Flutamide can sometimes affect the liver. Your doctor will do regular blood tests to check your liver. Tell your doctor straight away if you notice any yellowing of your skin or eyes.

Increased appetite

Flutamide may give you a bigger appetite and you might eat more than usual. It’s important to try to eat healthy foods, such as fruit and vegetables. This is so you don’t put on too much weight. Ask your doctor or nurse for advice about healthy eating.

Less common side effects of flutamide

Blurred vision

Rarely, flutamide can cause blurred vision. This may develop a few months after treatment has started. Let your doctor know about any changes to your vision.

Always let your doctor or nurse know about any side effects you have. There are usually ways in which they can be controlled or improved.

Other information about flutamide

Other medicines

Flutamide can affect how some other medicines work. If you’re taking medicines to thin your blood (such as warfarin) or theophylline to help with your breathing, let your doctor know before beginning treatment.

Tell your doctor about any medicines you are taking, including ones you can buy for yourself, complementary therapies, vitamins and herbal drugs.

Alcohol intake

Talk to your doctor or nurse about safe levels of alcohol intake while you are taking flutamide. Let them know if you need help or advice on staying within safe levels.


Your doctor will advise you not to father a child during treatment. This is because the drugs may harm a developing baby. It’s important to use effective contraception during and for a few months after treatment. You can talk to your doctor or nurse about this.

Medical treatment

If you need to go into hospital for any reason other than cancer, always tell the doctors and nurses that you are taking flutamide. Explain you are taking hormonal therapy that no one should stop or restart without advice from your cancer doctor. Tell them the name of your cancer doctor so they can ask for advice.