What is gefitinib (Iressa®)?

Gefitinib (Iressa®) is a targeted therapy drug used to treat non-small cell lung cancer (NSCLC). It is best to read this information with our general information about targeted therapies and the type of cancer you have.

Gefitinib belongs to a group of targeted therapy drugs known as cancer growth inhibitors.

Your doctor will talk to you about this treatment and its possible side effects before you agree (consent) to have treatment.

How gefitinib is given

During treatment you usually see a cancer doctor, a cancer nurse or specialist nurse, and a specialist pharmacist. This is who we mean when we mention a doctor, nurse or pharmacist in this information.

Gefitinib only works for cancers that have an abnormal form of a protein called epidermal growth factor receptor (EGFR). Tests are done on a sample of cancer cells from your lung to check the level of EGFR. This tells your doctor whether gefitinib is likely to help you.

Before and during treatment, a nurse or person trained to take blood (phlebotomist) will take a blood sample from you. This is to check the level of your blood cells and to check how well your liver and kidneys are working.

You will see a doctor or nurse before and during your treatment. They will ask you how you have been feeling.

Your course of treatment

Gefitinib is given as tablets. This means you can take it at home. Gefitinib may be given on its own, or with other drugs.

The nurse or pharmacist will give you the tablets to take home. Always take them exactly as explained. This is important to make sure they work as well as possible for you. Your nurse or pharmacist may also give you anti-sickness drugs and other medicines to take at home. Take all your drugs exactly as they have been explained to you.

You usually continue taking gefitinib for as long as it is still working, unless side effects are too bad.

Taking gefitinib tablets

You usually take gefitinib as a tablet once a day. Take the tablets at about the same time each day. Swallow them whole with a glass of water. You can take them with or without food.

If you have trouble swallowing tablets, put the tablet in half a glass of water and leave it to dissolve. Do not crush the tablets and do not use any other type of liquid. It may take 20 minutes to completely dissolve. Once the tablet has dissolved, drink it straight away. Then refill the glass with water and drink it to make sure you have taken all the gefitinib.

If you forget to take the tablets, you should take the missed dose as soon as you remember. But if there is less than 12 hours until your next dose, do not take the missed dose. Never take a double dose.

Do not take antacids or medicines to reduce stomach acid two hours before, or one hour after taking gefitinib. They can affect how gefitinib works.

Other things to remember about your tablets:

  • Keep them in the original package and at room temperature, away from heat and direct sunlight.
  • Keep them safe and out of sight and reach of children.
  • If you are sick just after taking the tablets, contact the hospital. Do not take another dose.
  • If your treatment is stopped, return any unused tablets to the pharmacist.

About side effects

We explain the most common side effects of this treatment here. We also include some less common side effects.

You may get some of the side effects we mention, but you are unlikely to get all of them. If you are also having treatment with other cancer drugs, you may have some side effects that we have not listed here. Always tell your doctor, nurse or pharmacist about any side effects you have.

Your doctor can give you drugs to help control some side effects. It is important to take them exactly as your nurse or pharmacist explains. This means they will be more likely to work for you. Your nurse will give you advice about managing your side effects. After your treatment is over, most side effects start to improve.

Serious and life-threatening side effects

Some cancer treatments can cause severe side effects. Rarely, these may be life-threatening. Your cancer doctor or nurse can explain the risk of these side effects to you.

Contact the hospital

Your nurse will give you telephone numbers for the hospital. If you feel unwell or need advice, you can call them at any time of the day or night. Save these numbers in your phone or keep them somewhere safe.

More information

We cannot list every side effect for this treatment. There are some rare side effects that are not listed. You can visit the electronic Medicines Compendium (eMC) to download a Patient Information Leaflet (PIL) for these drugs. The leaflet lists all known side effects.

Common side effects

Skin changes

You may develop a rash and your skin may become dry or flaky. Some people also feel itchy. These side effects are usually mild but sometimes can be more severe. If you have any skin changes, speak to your doctor or nurse. They can advise you about creams or lotions and give you medicines to relieve itching.

If you have more severe side effects, your doctor can stop your treatment with gefitinib for a few days to allow your skin to recover.


This treatment may cause diarrhoea. Diarrhoea means passing more stools (poo) than is usual for you, or having watery or loose stools. If you have a stoma, it will be more active than usual.

If you have diarrhoea:

  • try to drink at least 2 litres (3½ pints) of fluids each day
  • avoid alcohol, caffeine, milk products, high-fat foods and high-fibre foods
  • contact the hospital for advice.

Loss of appetite

This treatment can affect your appetite. Do not worry if you do not eat much for a day or two. But if your appetite does not come back after a few days, tell your nurse or dietitian. They will give you advice. They may give you food or drink supplements.

Sore mouth

You may get a sore mouth or mouth ulcers. This can make you more likely to get a mouth infection.

Use a soft toothbrush to clean your teeth or dentures in the morning, at night and after meals.

If your mouth is sore:

  • tell your nurse or doctor – they can give you a mouthwash or medicines to help
  • try to drink plenty of fluids
  • avoid alcohol, tobacco, and foods that irritate your mouth.

Feeling sick

You may feel sick in the first few days after treatment. Your doctor may give you anti-sickness drugs to help prevent or control sickness. Take the drugs exactly as your nurse or pharmacist tells you. It is easier to prevent sickness than to treat it after it has started.

If you feel sick, take small sips of fluids and eat small amounts often. If you continue to feel sick, or if you vomit more than once in 24 hours, contact the hospital as soon as possible. They will give you advice and may change the anti-sickness drug to one that works better for you.


Feeling tired is a common side effect. Try to pace yourself and plan your day so you have time to rest. Gentle exercise, like short walks, can give you more energy. If you feel sleepy, do not drive or operate machinery.

Effects on the liver

Treatment with gefitinib may cause changes in the way that your liver works. This will return to normal when treatment finishes. During treatment, your doctor will take regular blood samples to check your liver is working properly.

Less common side effects of gefitinib

Hair and nail changes

You may notice that the hair on your head and body becomes finer, curlier or more brittle. Some people have hair thinning or hair loss. These changes are usually temporary and gradually improve once treatment is over.

The nails on your hands or feet may become red, sore and brittle. Let your nurse or doctor know if this happens. Wearing gloves when using detergents or washing dishes can help protect your nails.

Eye problems

Your eyes may become dry and feel sore, or get red and inflamed. Some people’s eyes may water and they may be sensitive to light. Your doctor can give you eye drops to help with these problems. If you get pain in your eyes or have changes in your vision, let your doctor know immediately.

Some people find that their eyelashes grow longer and more curly than usual, but this isn’t common.

Bladder irritation

Your bladder may feel irritated during your treatment. You may notice a burning feeling when you pass urine, or you may need to go more often or more urgently. Tell your nurse or doctor if you have these symptoms. Drink around 2 litres (3½ pints) of fluids per day. Rarely, you may pass blood in your urine. If you notice this, tell your doctor straight away.

Breathing problems

This is an uncommon side effect that may affect a small number of people taking gefitinib. It may mean that you have an inflammation of the lungs, which can be serious.

Tell your doctor straight away if you have any of the following symptoms.

  • your breathing worsens
  • you have a cough or fever
  • you become breathless.

Bleeding problems

If you have any unusual bleeding while taking gefitinib, let your doctor know. This could include nosebleeds, bleeding gums or blood in your urine.

Severe tummy pain

Very rarely, gefitinib can cause a hole (perforation) in the small bowel or an inflamed pancreas. Contact your doctor immediately if you have severe pain in the tummy. It is also very important to let them know if you:

  • are bleeding from the back passage
  • have black stools
  • are vomiting up blood
  • have vomit that looks like coffee grounds.

Other information

Blood clot risk

Cancer and some cancer treatments can increase the risk of a blood clot. Symptoms of a blood clot include:

  • pain, redness or swelling in a leg or arm
  • breathlessness
  • chest pain.

If you have any of these symptoms, contact a doctor straight away.

A blood clot is serious, but can be treated with drugs that thin the blood. Your doctor or nurse can give you more information.

Other medicines

During treatment with gefitinib, you should not use the herbal remedy St John’s wort. This is because it can make gefitinib less effective. 

Some other medicines can be harmful to take when you are having gefitinib. These include medicines you can buy in a shop or chemist. Tell your cancer doctor about any drugs you are taking, including over-the-counter drugs, supplements, complementary therapies and herbal drugs.


Gefitinib contains lactose. If you have an intolerance to some sugars, talk to your doctor before taking this treatment.


Some cancer drugs can affect whether you can get pregnant or make someone pregnant. If you are worried about this, it is important to talk with your doctor before you start treatment.


Your doctor will advise you not to get pregnant or make someone pregnant while having this treatment. The drugs may harm a developing baby. It is important to use contraception during your treatment and for a while after treatment finishes. Your doctor, nurse or pharmacist can tell you more about this.


Women are advised not to breastfeed while having this treatment. This is because the drugs could be passed to the baby through breast milk.

Medical and dental treatment

If you need medical treatment for any reason other than cancer, always tell the doctors and nurses that you are having cancer treatment. Give them the contact details for your cancer doctor so they can ask for advice.

If you think you need dental treatment, talk to your cancer doctor or nurse. Always tell your dentist you are having cancer treatment.