Cyprostat (Cyproterone)

How does it work?

Cyprostat tablets contain the active ingredient cyproterone acetate, which is a type of medicine known as an anti-androgen. Cyproterone acetate is also available without a brand name, ie as the generic medicine.

Androgens are male hormones such as testosterone. They have many actions in the body and work by binding to receptors on cells and influencing the actions of these cells. Prostate cancers generally require the androgen testosterone in order to grow and spread.

Cyproterone acetate is used in the treatment of prostate cancer. It works by preventing testosterone from binding to androgen receptors in the prostate gland. It also acts on an area of the brain called the hypothalamus, which ultimately results in a reduction in the amount of testosterone produced by the body. It therefore starves prostate cancer cells of testosterone, which prevents them growing. Eventually the prostate tumour will shrink.

In the treatment of prostate cancer, cyproterone acetate is usually used in combination with another type of medicine known as a gonadorelin or LHRH analogue. LHRH analogues are one of the standard treatments for prostate cancer and include medicines such as buserelin, goserelin, leuprorelin and triptorelin. This class of medicines also work by decreasing testosterone levels and starving the cancer of testosterone. However, at the start of treatment they can cause a short-term increase in testosterone levels that makes the symptoms worse (flare) before they start to improve. Cyproterone acetate is used to block the effects of this increased testosterone and prevent the symptom flare during initial treatment with this type of medicine.

Cyproterone is also used on its own to treat prostate cancer in men for whom LHRH analogues or surgery are not suitable. In this case, cyproterone is taken long-term to reduce the symptoms of the cancer.

Lastly, cyproterone is used to control hot flushes that may arise in men who are having treatment with LHRH analogues, or who have had their testicles removed (orchidectomy) as part of their treatment.

What is it used for?

  • Prostate cancer.


  • This medicine can make you feel tired or weak and so may reduce your ability to drive or operate machinery safely. Do not drive or operate machinery until you know how this medicine affects you and you are sure it won't affect your performance.
  • This medicine may sometimes cause liver problems. For this reason, your doctor will want to monitor your liver function before you start treatment and regularly during treatment. This will usually require a blood test. You should let your doctor know if you experience any symptoms that could indicate a problem with your liver during treatment, so that your liver function can be checked. Symptoms that could indicate liver problems include unexplained itching, nausea and vomiting, severe abdominal pain, loss of appetite or flu-like symptoms; yellowing of the skin or eyes (jaundice); or unusually dark urine.
  • On rare occasions this medicine may cause a type of anaemia. For this reason, your doctor will want to do a blood test to check your blood cells before you start treatment and regularly during treatment.
  • The functioning of your adrenal glands should also be monitored regularly while you are taking this medicine.
  • This medicine will decrease your sperm count, but this change is reversible on stopping treatment. This medicine can also cause more of your sperms than usual to be abnormal in shape. It is possible that these abnormal sperms could produce birth defects. For this reason it is recommended that you use contraception to avoid fathering a child during your treatment. You should discuss this with your doctor before you start treatment with this medicine. The decrease in your sperm count will not happen immediately and you should not rely on this medicine for contraception at any time.

Use with caution in

  • Men who have ever had a blood clot in a vein (venous thromboembolism), eg in the leg (deep vein thrombosis) or in the lungs (pulmonary embolism).
  • Men who have ever had a blood clot in an artery, eg a stroke or mini-stroke (TIA) caused by a blood clot, or a heart attack.
  • Hereditary blood disorder called sickle cell anaemia.
  • Diabetes (particularly diabetes with complications, eg affecting the eyes, kidneys or blood circulation).
  • Advanced cancers.
  • Liver disease.
  • Long-term severe depression.

Not to be used in

  • Women.
  • Children.
  • People who have had a meningioma (a tumour in the protective membranes around the brain and spinal cord).

This medicine should not be used if you are allergic to any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Label warnings

  • Take this medication with or after food.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

Very common (affect more than 1 in 10 people)

  • Decreased sex drive (reversible on stopping treatment).
  • Impotence (reversible on stopping treatment).
  • Decreased sperm count (reversible on stopping treatment).
  • Reduced volume of ejaculation (reversible on stopping treatment).

Common (affect between 1 in 10 and 1 in 100 people)

  • Weight changes.
  • Depressive moods.
  • Restlessness.
  • Enlargement and tenderness of breasts (gynaecomastia).
  • Fatigue.

Uncommon (affect between 1 in 100 people and 1 in 1000 people)

  • Rash.

Rare (affect between 1 in 1000 and 1 in 10,000 people)

  • Shortness of breath.
  • Liver disorders.
  • Abnormal blood clots in the blood vessels (thromboembolism).
  • Reduced growth of body hair and increased growth of scalp hair.
  • Lightening of hair colour.
  • Severe allergic reaction.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

There are no significant interactions reported with this medicine.

Other medicines containing the same active ingredient


Cyproterone acetate tablets are also available without a brand name, ie as the generic medicine.