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Macmillan and Cancerbackup merged in 2008. Together we provide free, high quality information for people affected by cancer through our publications, website and phone service. Find out more|.
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This information is about a hormonal therapy| used to treat prostate cancer| called cyproterone acetate, which is also called Cyprostat®. Throughout this information we refer to it by its more commonly used name, Cyprostat.
This information should ideally be read with our general information about prostate cancer.
Cyprostat is a type of hormonal therapy used to treat prostate cancer. You will see your doctor regularly while you have this treatment so they can monitor its effects.
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 control the activity of cells and organs.
Most prostate cancers need supplies of the male hormone testosterone to grow. Testosterone is produced by the testes and the adrenal glands.
Prostate cancer cells have proteins called receptors that sex hormones attach to. Testosterone attaches to these receptors and causes cancer cells to grow.
Cyprostat has a structure similar to testosterone. It works by preventing testosterone from attaching (binding) to the receptors. Without testosterone, the cancer cells either grow more slowly or stop growing altogether. The cancer may shrink in size as a result.
Cyprostat is a tablet that is usually taken two or three times a day. The tablets should be taken after meals and swallowed whole with a glass of water. Doses should be evenly spaced throughout the day.
Cyprostat may be given on its own to treat prostate cancer if other treatments, such as surgery, are not suitable. It is also used to help prevent tumour flare.
Tumour flare is an increase in symptoms that can occur when other hormonal therapy drugs - known as LHRH analogues - are used to treat prostate cancer. LHRH analogues can cause an increase in testosterone levels in the first few days or weeks. This may cause a temporary increase in symptoms such as bone pain or difficulty passing urine. Cyprostat can prevent these symptoms from occurring.
Cyprostat may also be given to help reduce hot flushes| in men who are having LHRH analogues, or who have had their testicles removed (orchidectomy|) as part of their treatment.
Your doctor will discuss the length of treatment they feel is appropriate for your situation. Cyprostat is given for as long as it is effective in controlling your cancer. This may be for several months or years.
Each person's reaction to any medicine is different. Many people have very few side effects with Cyprostat, while others may experience more. The side effects described here won't affect everyone and may be different if you are having more than one drug.
We have outlined the most common side effects| but haven't included those that are rare and therefore unlikely to affect you. If you notice any effects which aren't listed here, discuss them with your doctor or nurse.
You may have some of the following side effects, to varying degrees:
Some men may notice slight breast swelling and tenderness,known as gynaecomastia. Your doctor can advise you about how this can be treated or prevented.
You may feel less energetic| than usual and it is important to take time to rest. The tiredness usually subsides when the treatment is stopped.
You may have a feeling of mild breathlessness| while you are taking Cyprostat. This will disappear when the treatment is stopped.
Nausea, vomiting and diarrhoea| are rare effects, which are usually mild and easily controlled. Nausea| can sometimes be relieved by taking the tablet with food. If you have any stomach pain that doesn't get better, let your doctor know.
Loss of sex| drive (libido) and erection difficulties (impotence) can occur in some men. These usually return to normal after stopping hormonal treatment. Talk to your doctor if these effects are a problem as they can prescribe drugs to help. Your doctor or nurse can discuss this with you.
You may experience mood swings or feel anxious. Talk to your doctor if this continues.
Cyprostat may increase your risk of getting a blood clot. If you have a history of blood clots, sickle cell anaemia or diabetes, let your doctor know as these conditions can increase your risk of getting a clot.
If you are taking Cyprostat and you develop any pain, warmth, swelling or tenderness in an arm or leg, or any chest pain, you should let your doctor know immediately.
Your doctor will take blood samples to test how well your liver is working. This is because Cyprostat can sometimes cause the amounts 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. Tell your doctor if you notice any yellowing of the skin or eyes.
If you are diabetic, your blood-sugar levels may be slightly higher than usual and may need more regular monitoring. Your GP or diabetes doctor should be able to help you manage this. Your blood-sugar levels should return to normal after you finish treatment with Cyprostat.
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.
This information is based on our Cyproterone acetate (Cyprostat®) fact sheet and has been compiled using information from a number of reliable sources, including:
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