Cyproterone acetate (Cyprostat®)

Cyproterone acetate is a hormonal therapy drug used to treat prostate cancer. It is also called Cyprostat®. It is usually called cyproterone. It works by interfering with the hormone testosterone. Cyproterone reduces the amount of testosterone in the body, which may shrink the prostate cancer or stop it growing.

Cyproterone is given as tablets. You usually have it as an outpatient. Your cancer doctor or nurse will tell you how often you will have it.

Hormonal therapies affect different people in different ways. Cyproterone can cause side effects, some of which can be serious. It’s important to tell your doctor or nurse straight away if you feel unwell or have severe side effects, including any we don’t mention. Your healthcare team can talk to you more about this and give you advice on how to manage any side effects you may have.

If you need to seek medical attention for any reason other than cancer, always tell the healthcare staff that you are having this hormonal therapy treatment.

What is cyproterone?

How cyproterone 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 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.

Cyproterone reduces the amount of testosterone made by your body. This reduces testosterone levels and may shrink the prostate cancer or stop it growing.

When cyproterone is given

You can have cyproterone on its own if other treatments, such as surgery, are not suitable.

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

You can have cyproterone for four weeks to reduce hot flushes that are caused by hormonal treatments, or if you have had your testicles removed (orchidectomy). Your doctor or nurse will explain why you are having cyproterone and how long you will take it for.

Taking your cyproterone tablets

You take cyproterone as tablets one to 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.

Do not 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 and at room temperature, away from heat and direct sunlight.
  • Keep them safe and out of the 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 cyproterone

We explain the most common side effects of cyproterone here. We also include some of the rare ones. 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 doctor or nurse about the side effects you have. They can prescribe drugs to help control side effects and give you advice about managing them. Don’t stop taking cyproterone 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 electronic Medicines Compendium (eMC).

Effects on sex life and sexuality

Most men have some loss of sex drive (libido) and erection difficulties (impotence) during hormonal therapy. These often return to normal after stopping the drug. Your doctor can prescribe treatments to help with erection difficulties. These treatments don’t increase sex drive. If you need support coping with sexual difficulties, your nurse or doctor can give you more information and refer you to specialist support services.

Weight changes

You may notice you have gained weight, or your ankles and legs may be swollen. This is due to fluid building up. Tell your doctor or nurse if this happens. The swelling will get better after your treatment ends.

Mood changes

You may experience mood swings or feel anxious, restless or depressed. This is more likely if you already have depression or low moods. Talk to your doctor or nurse if you notice this. They can give you support or advice about this.

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 can last for a few seconds or up to a couple of minutes. More severe flushes can last for 10 minutes or more. You may sweat, 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. You could try cutting down on nicotine, alcohol, and hot drinks that contain caffeine, such as tea and coffee. Hot flushes and sweats may lessen as your body adjusts to hormonal treatment. They usually stop completely a few months after treatment finishes.

Breast swelling or tenderness

You may notice slight breast swelling and tenderness. This is called gynaecomastia. Your doctor can advise you about how this can be prevented or treated.


You may feel tired with little energy while taking cyproterone. Try to pace yourself if you feel tired. Aim for a balance between having rest periods and being physically active. Doing exercise can reduce tiredness in men taking hormonal therapy. Ask your doctor or nurse what is safe for you to do.

If tiredness makes you feel sleepy, don’t drive or use machinery.


You may feel slightly short of breath while you are taking cyproterone. Talk to your doctor or nurse if this happens. This should stop when the treatment finishes.

Liver changes

Your doctor will take blood samples to test how well your liver is working. Cyproterone can sometimes cause changes in the way your liver works. If this happens, the drug will be stopped and your liver should return to normal. Tell your doctor if you notice any yellowing of your skin or eyes.

Change in blood sugar levels

If you have diabetes, your blood sugar levels may be slightly higher than usual and you may need to check them more regularly. Your doctor will talk to you about how to manage this. Your blood sugar levels should return to normal after you finish treatment with cyproterone.

Less common side effects of cyproterone

Blood clot (thrombosis)

Cyproterone may increase your risk of getting a blood clot if you have a history of clots, sickle cell anaemia or diabetes. If you are taking cyproterone and you have any pain, redness or swelling in an arm or leg, breathlessness or chest pain, let your doctor know immediately.

Skin changes

You may find that your skin gets dry. Some men develop a skin rash but this is usually mild and often gets better without treatment. Tell your doctor if you notice any skin changes.

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 cyproterone

Other medicines

Cyproterone can interact with other drugs. This includes medicines you can buy in a shop or chemist. Tell your doctor about any medicines you are taking, including ones you can buy for yourself, complementary therapies, vitamins and herbal drugs.


Cyproterone can affect your fertility (being able to father a child). If you are worried about this, you can talk to your doctor before treatment starts.


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 cyproterone. Explain you are taking a hormonal therapy that you should not stop or restart without advice from your cancer doctor. Tell them the name of your cancer doctor so they can ask for advice.