What is cyproterone?

Cyproterone acetate is a drug which is used in the treatment of prostate cancer. It is a type of hormonal therapy. Hormonal therapies interfere with the production or action of particular hormones in the body. Hormones are substances produced naturally in the body. They act as chemical messengers and help to control the activity of cells and organs.

How it is given

Cyproterone acetate is a tablet which is taken two or three times a day. Doses should be evenly spaced throughout the day.

How it works

Most prostate cancers need supplies of the male hormone testosterone to grow. This is produced by the testes and adrenal glands. On the surface of the prostate cancer cells are proteins called receptors. Cyproterone acetate has a structure similar to testosterone. It works by attaching itself to the receptors on the surface of the prostate cancer cells to block and prevent the attachment of testosterone. Without testosterone, the cancer cells either grow more slowly or stop growing altogether.

Cyproterone acetate may be given together with injections of another type of hormonal therapy drug such as goserelin, buserelin, triptorelin or leuprorelin. These drugs block the production of a hormone produced by the pituitary gland (leuteinising hormone), which stimulates the production of testosterone.

Possible side effects

Each person’s reaction to any medication is unique. Many people have very few side effects with cyproterone acetate, while others may experience more. The side effects described in this section will not affect everyone and may be different if you are having more than one drug.

We have outlined the most common side effects. However, we have not included those that are very rare and therefore extremely unlikely to affect you. If you notice any effects which you think may be due to the drug, but which are not listed here, please discuss them with your doctor or nurse.

You will see your doctor regularly while you have this treatment so that he or she can monitor the effects. This section should help you to discuss any queries about your treatment and its side effects with your doctor or nurse, as they are in the best position to help and advise you.

Some people may have some of the following side effects.

Breast tenderness or fullness  Some men may notice slight breast swelling and tenderness known as gynaecomastia. Your doctor can prescribe medicine to reduce any discomfort.

Tiredness and low mood  This is common during the first few weeks of treatment, but reduces with time.

Breathlessness  You may have a feeling of mild breathlessness while you are taking cyproterone acetate treatment. This will disappear if the treatment is stopped.

Nausea (feeling sick), vomiting and diarrhoea  These effects are uncommon and if they occur they are usually mild and easily controlled. Nausea can sometimes be relieved by taking the tablet with food.

Let your doctor know if you have any of these side effects as medication can be prescribed to help.

Lowering of libido (sex drive), and impotence (a loss of ability to have an erection)  This is uncommon. If it occurs sexual function will return to normal after stopping the drug. Your doctor or nurse can discuss this with you.

Effect on liver function  Your doctor will take blood samples to test how well your liver is working, as cyproterone acetate can sometimes cause the amount of particular chemicals produced by the liver to change. If this happens the drug will be stopped and the liver function will return to normal.

Length of treatment

Your doctor will discuss the length of treatment that they feel is appropriate for your situation. It is often given for several months or years.

Things to remember about cyproterone tablets

  • Keep the tablets in a safe place where children cannot reach them, as cyproterone could harm them.
  • If your doctor decides to stop the treatment, return any remaining tablets to the pharmacist. Do not flush them down the toilet or throw them away.
  • If you are sick just after taking the tablet tell your doctor as you may need to take another one.
  • If you forget to take your tablet, do not take a double dose. Let your doctor or nurse know. Don’t panic – levels of the drug in your blood will not change very much – but try not to miss more than one or two tablets in a row.
  • Remember to get a new prescription a couple of weeks before you run out of tablets and make sure you have plenty for holidays etc.
Cyproterone acetate (Cyprostat®)

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