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Degarelix (Firmagon)

This page tells you about the hormone therapy drug degarelix. There is information about


What degarelix is

Degarelix is a type of hormone therapy called a gonadatrophin releasing hormone blocker. It is a treatment for advanced hormone dependent prostate cancer. Hormone dependent means that that the cancer cells need a hormone in order to grow. Degarelix is pronounced deh-ga-rel-ix. It is also called Firmagon.

Prostate cancer depends on testosterone to grow. Drugs that stop the testes making testosterone can slow or stop the growth of prostate cancer cells. Degarelix works by blocking gonadatrophin releasing hormone receptors in the pituitary gland in the brain. The pituitary gland then stops producing luteinising hormone. Luteinising hormone triggers the testes to make testosterone.


How you have degarelix

You have degarelix as an injection just below the skin (subcutaneously) into the fatty tissue of your tummy (abdomen). The first time you have degarelix you have two injections. Then you have one injection once a month. You continue with the treatment for as long as it works.

The side effects associated with degarelix are listed below. You can use the links to find out more about each side effect. For general information, see our cancer drug side effects section.


Common side effects

More than 10 in every 100 men have one or more of these effects.


Occasional side effects

Between 1 and 10 in every 100 people have one or more of these.

  • Tiredness (fatigue) during treatment
  • Low levels of red blood cells (anaemia), which can cause tiredness and breathlessness
  • Weight increase happens in 7 out of 100 men (7%)
  • Difficulty sleeping
  • Dizziness and headaches
  • Diarrhoea – drink plenty of fluids and tell your doctor or nurse if diarrhoea becomes severe, or continues for more than 3 days
  • Feeling sick is usually well controlled with anti sickness medicines
  • Liver changes that are very mild and unlikely to cause symptoms – the liver will almost certainly go back to normal when treatment finishes, but you will have regular blood tests to check how well your liver is working
  • Flu like symptoms such as chills and fever for a few hours after the injection
  • Increased sweating, especially at night
  • Skin rashes
  • Pain in your back, joints and bones
  • Breast tenderness and swelling – this can be distressing so your doctor may suggest a small dose of radiotherapy before treatment to try to prevent it
  • Raised blood pressure

Rare side effects

Fewer than 1 in 100 people have these.

  • An allergic reaction to the drug – let your doctor or nurse know straight away if you feel breathless, or if you have swelling of your lips, face or throat
  • Changes in blood sugar levels – if you have diabetes you may need to check your blood sugar levels more often than usual
  • Raised cholesterol levels
  • Weight loss
  • Loss of appetite
  • Constipation – your doctor or nurse may give you laxatives to help prevent this but do tell them if you are constipated for more than 3 days
  • Swelling of the ankles and legs due to a build up of fluid (oedema) which is usually mild
  • Changes in your heart rhythm and blood pressure – your nurse or doctor will check your blood pressure and you will have regular ECGs
  • Skin changes, such as a rash, redness, and itching
  • Bone thinning may occur with long term treatment
  • You may find that the levels of sugar in your blood change – you will have regular blood tests. If you have diabetes you will need to take extra care when checking your blood sugar
  • Sadness that may develop into depression
  • Being sick
  • Stomach pain
  • A dry mouth – drink plenty of fluids if you have this
  • Aches and pains in muscles or bones
  • Muscle weakness
  • Pain when passing urine or needing to go urgently – let your doctor or nurse know if you have this

Important points to remember

You won’t get all these side effects. Any that you have may be mild. A side effect may get worse through your course of treatment. Or you may have more side effects as the course goes on. This depends on

  • How many times you've had a drug before
  • Your general health
  • How much of the drug you have (the dose)
  • Other drugs you are having

Talk to your doctor, pharmacist or nurse about all your side effects so they can help you manage them. They can give you advice or reassure you. Your nurse will give you a contact number to ring if you have any questions or problems. If in doubt, call them.

Tell your doctor about any other medicines you are taking, including vitamins, herbal supplements and over the counter remedies – some drugs can react together.

Degarelix is a relatively new drug in cancer treatment. This means that there is little information available at the moment about possible longer term side effects that it may cause. Tell your doctor or nurse if you notice anything that is not normal for you.


More information on degarelix

This page does not list all the very rare side effects of this treatment that are very unlikely to affect you. For further information look at the Electronic Medicines Compendium website at

If you have a side effect not mentioned here that you think may be due to this treatment you can report it to the Medicines Health and Regulatory Authority (MHRA) at

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Updated: 11 July 2013