Cyproterone acetate (Cyprostat)

Cyproterone acetate is a type of hormone therapy. You pronounce it as sy-proh-te-rone-a-suh- tayt. It’s also known as Cyprostat.   

You might have cyproterone acetate as a treatment for prostate cancer:

  • that has spread to other parts of the body (advanced prostate cancer) and you can’t have surgery or other medicines to treat your cancer
  • to treat hot flushes after surgery or medicine to stop the testicles producing the male sex hormone testosterone
  • to stop an increase in testosterone called a tumour flare

How does cyproterone acetate work?

Prostate cancer cells depend on the hormone testosterone to grow. Cyproterone acetate lowers levels of testosterone in the body and also blocks testosterone from reaching the cancer cells. This means it can slow or stop the growth of prostate cancer. It’s also known as anti androgen therapy.

How do you take cyproterone acetate?

You have cyproterone acetate as tablets. You take them either on their own or with another type of drug for prostate cancer called luteinising hormone (LH) blockers Open a glossary item

You take your tablets with a drink after meals and try to take them at evenly spaced times during the day. 

You must take tablets according to the instructions your doctor or pharmacist gives you.

Whether you have a full or an empty stomach can affect how much of a drug gets into your bloodstream.

You should take the right dose, no more or less. 

Talk to your healthcare team before you stop taking a cancer drug or if you miss a dose.

How often do you have cyproterone acetate?

You take cyproterone acetate tablets daily. The amount you have and how often you have them during the day depends on why you are taking them. 

Your doctor, nurse, or pharmacist will explain how many tablets you need to take and when to take them. Let them know if you have problems swallowing the tablets.

You take cyproterone acetate for as long as it is working, and the side effects aren’t too bad. 

Tumour flare 

You might take cyproterone acetate with a medicine called a luteinising hormone (LH) blocker. LH blockers stop the production of luteinising hormone, so the testicles stop making testosterone.  

LH blockers can take a few weeks to lower your testosterone. During this time your symptoms can get worse. This is called tumour flare. Cyproterone acetate helps stop the tumour flare from happening.

In this situation, you usually take cyproterone acetate for a few days before starting the LH blocker and stay on it for about 4 to 6 weeks.


You have blood tests before and during your treatment. They check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.

What are the side effects of cyproterone acetate?

Side effects can vary from person to person. They also depend on what other treatment you are having. 

When to contact your team

Your doctor, nurse, or pharmacist will go through the possible side effects. They will monitor you closely during treatment and check how you are at your appointments. Contact your advice line as soon as possible if:

  • you have severe side effects 

  • your side effects aren’t getting any better

  • your side effects are getting worse

Early treatment can help manage side effects better.

We haven't listed all the side effects here. Remember it is very unlikely that you will have all of these side effects, but you might have some of them at the same time.

Common side effects

These side effects happen in more than 10 in 100 people (more than 10%). You might have one or more of them. They include:

Loss of interest in sex (libido)

Talk to your doctor if you have this. You might be able to have some treatments to help with low libido. 

Erection problems

You might have problems getting an erection (impotence). Talk to your doctor or nurse if you have problems getting an erection. There are treatments that can help, such as medicines, vacuum pumps and injections or pellets. Your doctor or nurse can refer you to a specialist in this area.

Reduced sperm and ejaculate

Your sperm count and the amount you ejaculate reduce over a few months after you start taking cyproterone acetate. This usually goes back to normal after you stop your treatment. But the effects of long term treatment with cyproterone acetate on the sperm count are not yet known.

Ask your healthcare team about this before starting treatment. 

Occasional side effects

These side effects happen in between 1 and 10 out of every 100 people (between 1 and 10%). You might have one or more of them. They include:

  • breast swelling-rarely the breast can feel tender, lumpy or ooze white milky fluid 
  • tiredness and weakness (fatigue)
  • depression
  • mood changes
  • hot flushes or sweats
  • swelling in parts of the body (fluid build up)
  • weight loss and weight gain. The weight gain can be due to fluid build up
  • liver changes - symptoms include loss of appetite, feeling or being sick, and itchy skin- your skin may also look yellow. You have regular blood tests to check for this. Very rarely there is a risk of developing cancer of the liver or non cancerous lumps in the liver that may cause bleeding in the tummy (abdomen) 
  • shortness of breath

Rare side effects

These side effects happen in fewer than 1 in 100 people (fewer than 1%). You might have one or more of them. They include:

  • skin rash
  • an allergic reaction that can cause a rash, shortness of breath, redness or swelling of the face and dizziness. This can be life threatening. Call your advice line straight away if you have any of these symptoms
  • risk of developing a type of brain tumour (meningioma)

Other side effects

There isn't enough information to work out how often these side effects might happen. You might have one or more of them. They include:

  • blood clots that can be life threatening; signs are pain, redness and swelling where the clot is. Feeling breathless can be a sign of a blood clot in the lung. Contact your advice line or doctor straight away if you have any of these symptoms
  • weakening and thinning of the bones (osteoporosis)
  • breathlessness and looking pale due to a low number of red blood cells (anaemia)
  • dryness of the skin and scalp
  • changes to how well the hair grows and loss of hair

Coping with side effects

We have more information about side effects and tips on how to cope with them.

What else do I need to know?

Other medicines, foods and drink

Cancer drugs can interact with medicines, herbal products, and some food and drinks. We are unable to list all the possible interactions that may happen. An example is grapefruit or grapefruit juice which can increase the side effects of certain drugs.

Tell your healthcare team about any medicines you are taking. This includes vitamins, herbal supplements and over the counter remedies. Also let them know about any other medical conditions or allergies you may have.


Cyproterone acetate may harm a baby developing in the womb. It is important not to get someone pregnant while you are having treatment and for some time after finishing treatment. This can be up to 20 months but it varies from person to person.  

Before you start, talk to your doctor or nurse about effective contraception. They can tell you when to start and how long you should continue to use it. Let them know straight away if your partner falls pregnant while you're having treatment.


This drug can cause infertility, but this is often temporary. Fertility can return in a few months or longer after treatment ends. The time it takes can vary from person to person. The effects of long term treatment on fertility are not known.

Talk to your doctor before starting treatment if you think you may want to have a baby in the future.

Treatment for other conditions

If you are having tests or treatment for anything else, always mention your cancer treatment. For example, if you are visiting your dentist.

More information about this treatment

For further information about this treatment and possible side effects go to the electronic Medicines Compendium (eMC) website. You can find the patient information leaflet on this website.

You can report any side effect you have to the Medicines Health and Regulatory Authority (MHRA) as part of their Yellow Card Scheme.

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