Cyproterone acetate (Cyprostat ®)
Cyproterone acetate is a hormonal therapy, which is also called Cyprostat®. It is used to treat prostate cancer. Throughout this information we refer to it by its more commonly used name, Cyprostat.
Cyprotstat is a type of hormonal therapy used to treat prostate cancer.
Hormones are substances produced naturally in the body. They act as chemical messengers and help control the activity of cells and organs. Hormonal therapies work by interfering with the production or action of particular hormones in the body.
You will see your doctor regularly while you have this treatment so they can monitor its effects. This information should help you discuss any queries about your treatment and its side effects with your doctor or specialist nurse.
Most prostate cancers need supplies of a hormone called 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.
How Cyprostat is taken
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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.
When Cyprostat is given
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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 of treatment. 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 (called 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.
Loss of sex drive (libido) and erection difficulties (impotence) can occur. 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.
Breast tenderness or fullness
Occasionally some men notice slight breast swelling or 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.
You may experience mood swings or feel anxious or depressed. Talk to your doctor if this continues.
There are a number of ways to help reduce hot flushes and sweats. Some men find it helps to cut down on tea, coffee, nicotine and alcohol. Tell your doctor if hot flushes are causing you any problems, as research suggests that some treatments may help to control them.
Effect on liver function
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 liver function will return to normal. Tell your doctor if you notice any yellowing of the skin or eyes.
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.
Things to remember about Cyprostat tablets
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It's advisable not to father any children while you are being treated with Cyprostat as the developing baby may be affected. Use effective contraception while you're taking Cyprostat.
Keep the tablets in a safe place, out of the reach of children.
If your doctor decides to stop the treatment, return any remaining tablets to the pharmacist. Don't flush them down the toilet or throw them away.
Don't worry if you forget to take your tablet. Do not take a double dose. The 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 few weeks before you run out of tablets and make sure that you that have plenty for holidays.
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If you’re admitted to hospital for a reason not related to the cancer, it’s important to tell the doctors and nurses looking after you that you are having hormonal treatment. You should tell them the name of your cancer specialist so that they can ask for advice.
It’s a good idea to know who you should contact if you have any problems or troublesome side effects when you’re at home.
Change in blood-sugar levels
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.
Blood clot (thrombosis)
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.
Watch videos about prostate cancer treatment
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Dr Nick Plowman explains the treatment options for early prostate cancer, including watchful waiting and hormonal therapies.
See more about the options if you have advanced prostate cancer. Hormonal therapy is an important treatment.
This section has been compiled using information from a number of reliable sources, including:
British National Formulary. 63rd edition. 2012. British Medical Association and Royal Pharmaceutical Society of Great Britain.
electronic Medicines Compendium (eMC). http://www.medicines.org.uk (accessed September 2012).
Sweetman, et al. Martindale: The Complete Drug Reference. 37th edition. 2011 Pharmaceutical Press.
Thank you Kavita Kantilal, E-Prescribing Pharmacist, and all the people affected by cancer who reviewed this edition. Reviewing information is just one of the ways you could help when you join our Cancer Voices network.