This information is about a hormonal therapy called triptorelin that is used in the treatment of advanced prostate cancer. It should ideally be read with our general information about prostate cancer.

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.

Most prostate cancers need supplies of the male hormone testosterone to grow. Testosterone is produced by the testes and the adrenal glands.

Triptorelin acts by lowering the level of testosterone in the body. The testes will only make testosterone if told to do so by another hormone called luteinising hormone, which is produced by a part of the brain known as the pituitary gland. Triptorelin reduces the production of luteinising hormone, so the levels of testosterone fall. This may result in shrinkage or slowing down of the growth of the cancer. There may be a brief increase in testosterone levels in the first few days or weeks of starting treatment.

Triptorelin is either given by injection into the muscle (intramuscularly) of the buttock, or as an injection under the skin (subcutaneously). It can be given as a monthly injection or as a longer-acting preparation every three months. It can be given by your GP or practice nurse at the surgery. If you are not able to visit the surgery, a district nurse can give you the injection at home.

Sometimes people may find the injection slightly uncomfortable and may notice an area of redness or darker skin at the injection site afterwards. If you find the injection very uncomfortable you can have a tiny amount of local anaesthetic to numb the area before the triptorelin is given.

Each person's reaction to any medication is different. Many people have very few side effects with triptorelin while others may experience more. 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 that you think may be due to the drug, but which are not listed in this information, please discuss them with your doctor or nurse.

You will see your doctor regularly while you have this treatment so that they can monitor the effects. This information 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:

Tumour flare There may be a temporary increase in testosterone levels in the first few days or weeks of starting triptorelin. Some people may have an increase in symptoms such as bone pain. Rarely, other problems may occur due to a temporary increase in the size of the tumour. This is known as tumour flare. If you experience any problems, you will need to let your doctor know. Other types of hormonal therapy such as cyproterone acetate, flutamide or bicalutamide may be given for the first few weeks of starting triptorelin to prevent tumour flare from occurring.

Hot flushes and sweating These can be quite common, but many people find that hot flushes wear off after a period of time. Let your doctor know if hot flushes are causing you any problems, as medicines can sometimes be prescribed to counteract them. There are a number of ways to help reduce hot flushes and sweats. It can be useful to avoid or cut down on tea, coffee, nicotine and alcohol.

Some people find that complementary therapies help. Your GP may be able to give you details about obtaining these on the NHS.

Loss of sex drive (libido) and erection difficulties (impotence) This is a rare side effect and will usually return to normal after stopping the drug. Your doctor or nurse can discuss this with you.

Breast tenderness or fullness Men may sometimes notice slight breast swelling and tenderness known as gynaecomastia. Your doctor can prescribe medicines to reduce any discomfort.

Feeling sick (nausea), being sick (vomiting) and mild diarrhoea Feeling sick, vomiting and mild diarrhoea is rare and if they occur are usually mild and easily controlled. Let your doctor know if you have any of these side effects as medicines can be prescribed to help.

What if I miss an injection? Missing an injection by 2–3 days should not make a great difference, but it is important to remember that the benefits of the injections are designed to last 4 or 12 weeks, depending on which preparation you are prescribed, so you should have them as regularly as possible.

Length of treatment Your doctor will discuss the length of treatment that they feel is appropriate for your situation. Triptorelin is often given for several months or years. Treatment may continue as long as it is controlling the cancer.

This section has been compiled using information from a number of reliable sources including:

• Martindale: The Complete Drug Reference (35th edition). Sweetman et al. Pharmaceutical Press, 2007.
• British National Formulary (54th edition). British Medical Association and Royal Pharmaceutical Society of Great Britain, September 2007.

For further references, please see the general bibliography.