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Flutamide (Drogenil)

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This page gives information about the hormone therapy drug flutamide and its possible side effects. There are sections about


What flutamide is

Flutamide is a type of hormone therapy drug called an anti androgen. It is a treatment for advanced prostate cancer.


How flutamide works

Prostate cancer depends on the male sex hormone, testosterone, to grow. Testosterone is an androgen. Prostate cancer cells have special proteins known as receptors that take up testosterone. Anti androgens such as flutamide stop the testosterone triggering the cells to divide and grow. This can slow the growth of the cancer or shrink it.

Some men take flutamide for a short time with another type of drug for prostate cancer called a luteinising hormone (LH) blocker

LH blockers include 

If you are having flutamide with one of these drugs, it is to stop what is called a flare reaction. When you first start on LH blockers you actually make more testosterone for the first few days or weeks. This soon settles down, and after a few weeks you stop making testosterone. Flutamide helps to reduce any cancer symptoms caused by the short term increase in testosterone.


How you have flutamide

You take flutamide as a tablet, 3 times a day. You swallow it whole with a glass of water. Try to take it at evenly spaced times during the day. If you are having it to stop a flare reaction, you take it for a few days before starting the LH blocker, and stay on it for about 4 to 6 weeks.

It is very important that you take tablets according to the instructions your doctor or pharmacist gives you. For example, whether you have a full or empty stomach can affect how much of a drug gets into your bloodstream. You should take the right dose, not more or less. And never stop taking a cancer drug without talking to your specialist first.

We've listed the side effects associated with flutamide below. You can use the links to find out more about each side effect. Where there is no link, please use the search box at the top of the page. Or you can look in the cancer drug side effects section. The side effects may be different if you are also taking other cancer treatment drugs.


Common side effects

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

  • Hot flushes and sweats affect 3 out of 5 men treated (60%). Unfortunately, some men have them for as long as they stay on the treatment. Tell your doctor or nurse if they are difficult for you to cope with
  • Lowered interest in having sex (libido) and problems getting an erection (impotence) – these affect about 3 out of 10 (30%) men. These effects may stop after you finish treatment
  • Breast tenderness and swelling – this can affect about 1 out of 10 (10%) men treated, and can be distressing. Rarely, you may have some fluid leaking from your breast (galactorrhoea) with the swelling
  • You may not be able to father a child immediately after treatment with this drug, but this effect is usually temporary. It is important to talk to your doctor about your fertility before starting treatment if you think you may want to have a baby in the future. You may be able to store sperm before starting treatment

Occasional side effects

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

  • Tiredness and weakness (fatigue) usually improves within a few weeks of starting treatment
  • Sadness usually improves within a few weeks of treatment – if it goes on for longer, talk to your doctor or nurse about getting some support
  • Feeling or being sick affects 1 in 10 men treated (10%) – it is usually mild and can be controlled by anti sickness medicines
  • Diarrhoea affects about 1 in 10 men (10%) – it is usually mild but if you have diarrhoea you need to make sure you drink plenty of fluids
  • A reduced number of red blood cells (anaemia) – about 1 in 20 men (5%) will become anaemic
  • Liver changes that are very mild and  unlikely to cause symptoms – they will almost certainly go back to normal when treatment is finished. You will have regular blood tests to check how well your liver is working. If you have itchy skin, your urine gets darker, or your skin and eyes look yellow, contact your doctor or nurse straight away
  • Difficulty sleeping

Rare side effects

Fewer than 1 in 100 people have these.

  • Blurred vision – your vision may become blurred a few months after you start treatment
  • A skin rash and, very rarely, increased sensitivity to the sun (photosensitivity)
  • Dizziness – do not drive or operate machinery if you have this
  • Headaches

Important things to remember

The side effects above may be mild or more severe. A side effect may get better or worse through your course of treatment, or more side effects may develop as the course goes on. This depends on

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

Coping with side effects

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.

Other medicines

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


It is best to drink only limited amounts of alcohol while taking this treatment.


This drug may harm a baby developing in the womb. It is important not to father a child while you are having treatment and for a few months afterwards. Talk to your doctor or nurse about effective contraception before starting treatment.


Related information

On this website you can read about

hormone therapy

anti androgen


More information about flutamide

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 www.medicines.org.uk.

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 www.mhra.gov.uk.

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Updated: 27 August 2014