This information is about a hormonal therapy called flutamide that is used to treat prostate cancer. It should ideally be read with our general information about prostate cancer.

Flutamide is a type of hormonal therapy that is used in the treatment of prostate cancer.

There are several types of hormonal therapies. Your doctor can discuss with you which is best for your situation.

Hormonal therapies interfere with the production or action of particular hormones in the body. Hormones are substances which are 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 adrenal glands.

On the surface of the prostate cancer cells are proteins called receptors. Flutamide has a structure similar to testosterone. It works by blocking and preventing testosterone from attaching itself to the receptors on the prostate cancer cells. Without testosterone, the cancer cells either grow more slowly or stop growing altogether.

Flutamide is a tablet which is taken three times a day. Doses should be evenly spaced throughout the day.

Flutamide is given to treat prostate cancer that has spread to other parts of the body (advanced prostate cancer). It may be given on its own or in combination with injections of goserelin, buserelin or leuprorelin, which are hormonal therapy drugs known as LHRH analogues. LHRH drugs block the production of a hormone produced by the pituitary gland (leuteinising hormone) which normally stimulates the production of testosterone.

Flutamide can also be used to help prevent tumour flare, which can occur when LHRH analogues are given. LHRH analogues may cause a temporary increase in testosterone levels, which can cause an increase in symptoms such as bone pain, or difficulty passing urine. This is known as tumour flare and flutamide may help to prevent these symptoms.

Each person's reaction to any medication is different. Many people have very few side effects with flutamide 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:

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

Diarrhoea This occurs quite commonly and may be accompanied by abdominal cramps. Diarrhoea can usually be easily controlled but occasionally it may be severe. It is important to tell your doctor if this occurs, as it may be necessary to reduce or discontinue the flutamide and consider other types of hormonal therapy.

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

Tiredness You may feel less energetic than usual and it is important to take time to rest. This usually subsides when the flutamide treatment is stopped.

Effect on liver function Your doctor will take blood samples to measure how well your liver is working, as flutamide can sometimes cause a change in the amount of particular chemicals produced by the liver. If this happens the drug will be stopped and the liver function usually returns to normal.

Blurred vision A rare side effect of flutamide is blurred vision. This may develop a few months after treatment has started.

Feeling sick (nausea) or being sick (vomiting) This is rare. If it occurs it can usually be effectively treated. Tell your doctor if you have nausea or vomiting.

Your doctor will discuss the length of treatment that they feel is appropriate for your situation. Flutamide is often given for several months or even years. Treatment with flutamide may continue for as long as it is effective in controlling your cancer.

Flutamide may interact with other medicines. Let your doctor know about any medications you are taking, including non-prescribed drugs such as complementary therapies, vitamins and herbal drugs.

• Keep the tablets in a safe place where children cannot reach them, as flutamide 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 worry – 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. Make sure that you have plenty for holidays.

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.