Cyproterone acetate (Cyprostat) | Cancer Research UK
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What cyproterone acetate is

Cyproterone is a hormone therapy used to treat prostate cancer. It has the brand name Cyprostat. It is a type of drug called an anti androgen. 

You take cyproterone acetate either on its own, or with another type of drug for prostate cancer called a luteinising hormone (LH) blocker. 

LH blockers include 

  • Goserelin (Zoladex)
  • Leuprorelin (Prostap)
  • Triptorelin (Decapeptyl SR, Gonapeptyl Depot)

If you are having cyproterone acetate with a luteinising hormone blocker, it is to stop what is called a flare reaction. When you first start taking LH blockers you actually make more testosterone for the first few days or weeks, which increases the symptoms of the prostate cancer. This soon settles down, and after a few weeks you stop making testosterone. Cyproterone acetate helps to reduce any cancer symptoms caused by this temporary increase in testosterone.

Cyproterone can also help to reduce hot flushes in men who have had their testicles removed as a treatment for prostate cancer or who are taking luteinising hormone blockers.


How cyproterone works

Prostate cancer cells depend on the hormone testosterone in order to grow. Cyproterone lowers levels of testosterone in the body and also blocks testosterone from reaching the cancer cells. It slows or stops the growth of prostate cancer.


How you have cyproterone

You take cyproterone acetate as a tablet 2 or 3 times a day, with water after meals. Try to take it at evenly spaced times during the day. If you are having it to stop a flare reaction, you take it for a few days before starting the luteinising hormone blocker, and stay on it for about 4 to 6 weeks.

It is very important that you take tablets according to the instructions your doctor or pharmacist gives you. For example, whether you have a full or empty stomach can affect how much of a drug gets into your bloodstream. You should take the right dose, not more or less.

If you accidentally take too much cyproterone let your doctor or nurse know straight away. If you forget to take a dose, don't take extra tablets to make up for it. Just take the next dose when it is due. When you stop taking cyproterone you need to reduce the dose gradually. Your doctor will tell you exactly how to do this. Never stop taking a cancer drug without talking to your specialist first. 


Tests during treatment

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


About side effects

We've listed the side effects associated with cyproterone. You can use the links to find out more about each side effect. Where there is no link, please go to our information about cancer drug side effects or use the search box at the top of the page.

You may have a few side effects. They may be mild or more severe. A side effect may get better or worse through your course of treatment. Or more side effects may develop as the course goes on. This depends on

  • How many times you've had the drug before
  • Your general health
  • The amount of the drug you have (the dose)

The side effects may be different if you are having cyproterone with other medicines.

Tell your doctor or nurse straight away if any of the side effects get severe.


Temporary side effects when treatment starts

If you are taking cyproterone with other hormone therapy drugs you may have a temporary increase in symptoms for a few weeks, including 

  • Increased pain or difficulty passing urine
  • Bone pain
  • Back pain  
  • Blood in the urine  
  • A pins and needles feeling in the legs

Tell your doctor or nurse if you have any of these effects.


Common side effects

More than 10 in every 100 people have one or more of these.


Occasional side effects

Between 1 and 10 in every 100 people have one or more of these.

  • Tiredness (fatigue) and weakness – this usually improves within a few weeks of starting treatment. Don't drive or operate machinery if you feel very tired and weak
  • Sadness or depression – this usually improves within a few weeks of treatment. If it goes on for longer, talk to your doctor or nurse about getting some help
  • Hot flushes and sweating
  • Fluid retention causing ankle and or finger swelling
  • High blood pressure
  • Weakening of the bones (osteoporosis)
  • Gaining or losing weight

Rare side effects

Fewer than 1 in 100 people have these.

  • Changes in how your liver works – you will have blood tests to check for this. Your liver nearly always goes back to normal after treatment ends
  • A reduced number of red blood cells leading to tiredness and breathlessness
  • Blood clots – there is a slightly increased risk of developing a blood clot (thrombosis) when you are taking cyproterone. If you’ve had a blood clot in the past tell your doctor. They may want to change you to another type of hormone therapy. Let your doctor or nurse know straight away if you have a red, hot, swollen area  on your leg or if you suddenly develop a cough, breathlessness or chest pain
  • There is a small risk of developing a type of brain tumour called a meningioma if you take cyproterone acetate for a long time.  If you have had a meningioma or you develop one you should not take this drug
  • Some people have an allergic reaction to the drug when they first take it – let your doctor or nurse know straight away if you have a sudden rash or swelling of the lips, face or throat

Important points to remember

Talk to your doctor, pharmacist or nurse about all your side effects so they can help you manage them. They can give you advice or reassure you. Your nurse will give you a contact number to ring if you have any questions or problems. If in doubt, call them.

If you have diabetes

If you have diabetes, cyproterone acetate may affect your blood sugar levels. You need to check your blood sugar more often when you are having cyproterone.

Other medicines and foods

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and over the counter remedies. Some drugs can react together. 

Avoid drinking alcohol while having cyproterone treatment because alcohol reduces the effect of the cyproterone tablets.


This drug may harm a baby developing in the womb. It is important not to father a child while you are having treatment and for a few months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.


More information on cyproterone acetate

This page does not list all the very rare side effects of this treatment that are very unlikely to affect you. For further information look at the Electronic Medicines Compendium website at

If you have a side effect not mentioned here that you think may be due to this treatment you can report it to the Medicines Health and Regulatory Authority (MHRA) at

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Updated: 26 August 2015