Gefitinib (Iressa) | Cancer Research UK
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What gefitinib is

Gefitinib is pronounced jeh-fit-ih-nib. It is also known by its brand name Iressa. 

It is a treatment for non small cell lung cancer that has spread into surrounding tissues (locally advanced cancer) or to other parts of the body. Gefitinib is also used in clinical trials for other types of cancer.


How gefitinib works

Gefitinib is a type of biological therapy called a tyrosine kinase inhibitor (TKI). It blocks a type of protein called tyrosine kinase from sending signals that make the cancer cells grow.

In order for gefitinib to work, the cancer cells need to have receptors for a protein called epidermal growth factor (EGFR).


How you have gefitinib

Gefitinib is a tablet. You take it with a glass of water. If you can’t swallow tablets you can put it in half a glass of water and leave it to dissolve. This usually takes about 20 minutes and you will need to swill it round a bit. It is important to make sure that you drink all of the liquid.

You have gefitinib once a day and need to take it at about the same time each day. Avoid taking anti acid medicines 2 hours before taking gefitinib and for 1 hour afterwards. 

You usually carry on taking gefitinib for as long as it works. 

It is very important that you take tablets according to the instructions your doctor or pharmacist gave you. Whether you have a full or empty stomach, for example, can affect how much of a drug gets into your bloodstream. You should take the right dose, not more or less. 

If you take too many tablets by accident, let your doctor or pharmacist know straight away. 

If you forget to take a tablet and it is 12 hours or more before the next dose, take the missed tablet as soon as you remember. If it is less than 12 hours until the next dose, skip the next tablet and then take the next tablet at the usual time. Don't take a double dose to make up for the forgotten dose.


Tests during treatment

You have blood tests before starting treatment and regularly during your treatment. The tests check your levels of blood cells and other substances in the blood. They also check how well your liver and kidneys are working.


About side effects

We've listed the side effects associated with gefitinib. You can use the links to find out more about each side effect. Where there is no link, please go to our information about cancer drug side effects or use the search box at the top of the page.

You may have a few side effects. They 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)

The side effects may be different if you are having gefitinib with other medicines.

Tell your doctor or nurse straight away if any of the side effects get severe.


Common side effects

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

  • Skin changes – up to 3 out of 4 people (75%) have a rash or red, dry, itchy skin or acne. Rarely, this may be severe and you may need to stop treatment for a while
  • Diarrhoea affects 5 out of 10 people (50%) – drink plenty of fluids. Tell your doctor or nurse if it becomes severe or continues for more than 3 days
  • Feeling weak, and lacking in energy and strength
  • Feeling or being sick happens in about 1 out of every 10 people (10%) but is usually well controlled with anti sickness medicines
  • Loss of appetite happens in about 1 out of 10 people (10%)
  • A sore mouth occurs in about 1 out of 10 people (10%)
  • Liver changes that are very mild and unlikely to cause symptoms may occur. The liver will almost certainly go back to normal when treatment ends
  • Loss of fertility – you may not be able to become pregnant or father a child after this treatment. Talk to your doctor before starting treatment if you think you may want to have a baby in the future. Men 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.

  • Increased risk of bleeding – this includes nosebleeds and bleeding from your gums. If you notice blood in your urine, poo, or in your vomit, contact your doctor or nurse straight away
  • Eye problems including blurred vision, sore, red, itchy, dry eyes (conjunctivitis), or infection– tell your doctor or nurse straight away if you have this. Eye drops can help
  • Red and sore eyelids or ingrowing eyelashes
  • Brittle or loose nails
  • Hair thinning
  • Kidney changes that are mild and unlikely to cause symptoms may occur. These will almost certainly go back to normal when treatment is finished
  • A high temperature (fever)
  • Severe lung problems occur in 1 in 100 people (1%) – if you have a cough, high temperature and are short of breath contact your treatment centre urgently
  • Inflammation of the bladder lining (cystitis) causing a burning feeling when you pass urine or making you need to pass urine often. Let your doctor or nurse know if you have this

Rare side effects

Fewer than 1 in 100 people have these effects so they are rare but can be serious. Tell your doctor or nurse straight away if you have any of them

  • Eye pain – if this is severe your doctors may reduce the dose or stop treatment
  • Inflammation of the pancreas causing severe pain in the upper part of the abdomen and severe nausea and vomiting
  • Inflammation of the liver, which makes you feel very ill – you may also have yellowing of the skin and eyes (jaundice)
  • A hole in the wall of the stomach or bowel causing sudden, severe pain or blood in your vomit or poo

Important points to remember

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.

Pregnancy and contraception

This drug may harm a baby developing in the womb. It is important not to become pregnant or 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.


Don't breastfeed during this treatment because the drug may come through in the breast milk.

Lactose intolerance

Gefitinib tablets contain a type of sugar called lactose. Contact your doctor before taking this medicine if you have an intolerance to lactose.



You should not have immunisations with live vaccines while you are having treatment or for at least 6 months afterwards. In the UK, these include rubella, mumps, measles (usually given together as MMR), BCG, yellow fever and Zostavax (shingles vaccine).

You can have other vaccines, but they may not give you as much protection as usual until your immune system has fully recovered from your treatment. It is safe to have the flu vaccine.

It is safe for you to be in contact with other people who've had live vaccines as injections. There can be problems with vaccines you take by mouth (oral vaccines), but not many people in the UK have these now. So there is usually no problem in being with any baby or child who has recently had any vaccination in the UK. You might need to make sure that you aren't in contact with anyone who has had oral polio, cholera or typhoid vaccination recently, particularly if you live abroad.


More information on gefitinib

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: 8 October 2015