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Trade/other name(s): Iressa, ZD1839

Why would this drug be used?

This drug is used to treat some types of non-small cell lung cancer. It is used only in patients who are already taking it and being helped by it. Gefitinib is also being studied for use against other cancers.

How does this drug work?

Gefitinib is a type of targeted therapy known as a tyrosine kinase inhibitor. Its target is a tyrosine kinase protein called epidermal growth factor receptor (EGFR), which is located on the surface of certain cells in the body. Some cancers have higher than normal numbers of these receptors on their surfaces. Gefitinib blocks the receptor from sending a message to tell the cell to grow and divide.

Before taking this medicine

Tell your doctor…

  • If you are allergic to anything, including medicines, dyes, additives, or foods.
  • If you have any type of liver disease (including hepatitis). This drug is cleared from the body mainly by the liver. Reduced liver function might result in more drug than expected staying in the body, which could lead to unwanted side effects. Your doctor may need to adjust your dose.
  • If you have any other medical conditions such as kidney disease, heart disease, congestive heart failure, lung problems, diabetes, gout, or infections. These conditions may require that your medicine dose, regimen, or timing be changed.
  • If you are taking any blood-thinning medicines (see "Interactions with other drugs" below).
  • If you have any type of heart problem (including long Q-T syndrome), or if you are taking medicines to help your heart rhythm. This drug may affect the rhythm of the heart.
  • If you are pregnant, trying to get pregnant, or if there is any chance of pregnancy. This drug can cause problems with the fetus if taken at the time of conception or during pregnancy. Check with your doctor about what kinds of birth control can be used with this medicine. Pregnant women should only continue taking this drug if the potential benefit to the mother outweighs the risk to the fetus.
  • If you are breast-feeding. While no studies have been done, this drug may pass into breast milk and affect the baby. Breast-feeding is not recommended during treatment with this drug.
  • If you think you might want to have children in the future. It is not known whether or not this drug can affect fertility. Talk with your doctor about the possible risk with this drug and the options that may preserve your ability to have children.
  • About any other prescription or over-the-counter medicines you are taking, including vitamins and herbs. In fact, keeping a written list of each of these medicines (including the doses of each and when you take them) with you in case of emergency may help prevent complications if you get sick.

Interactions with other drugs

Gefitinib can interact with a number of drugs and supplements, which may either raise or lower the level of gefitinib in your blood.

The following drugs can cause gefitinib to build up in the body, raising the risk of serious side effects:

  • the antidepressant nefazodone (Serzone)
  • the antibiotics erythromycin (EES), clarithromycin (Biaxin), telithromycin (Ketek), and similar drugs
  • anti-fungal antibiotics such as ketoconazole (Nizoral), itraconazole (Sporanox), voriconazole (Vfend)
  • HIV drugs such as indinavir, ritonavir, fosamprenavir, nelfinavir, atazanavir, and others

Do not start or stop taking these medicines while on gefitinib without talking with the prescribing doctor(s) about all of the medicines you take, including gefitinib.

These drugs and supplements can lower the levels of gefitinib in the blood and make it less effective:

  • anti-seizure drugs carbamazepine (Tegretol), phenobarbital (Luminal), and phenytoin (Dilantin)
  • TB drugs rifampin (Rifadin, Rimactane; also in Rifamate and Rifater) and rifabutin (Mycobutin)
  • the steroid drug dexamethasone (Decadron)
  • St. John's wort (herbal dietary supplement)

If you need to take these drugs, your doctor may need to adjust your dose of gefitinib.

Drugs used to treat heartburn, reflux, or ulcers reduce acid levels in the stomach. This may affect the amount of gefitinib your body can absorb. Tell your doctor if you are taking:

  • any H2 blocker such as cimetidine (Tagamet), ranitidine (Zantac), famotidine (Pepcid), or nizatidine (Axid)
  • any proton pump inhibitor such as omeprazole (Prilosec), esomeprazole (Nexium), pantoprazole (Protonix), rabeprazole (Aciphex), or lansoprazole (Prevacid)

If you take warfarin (Coumadin), your doctor will watch your clotting times closely while you are taking gefitinib.

There may be more drugs that interact with gefitinib. Check with your doctor, nurse, or pharmacist about any other medicines, herbs, and supplements you are taking, and whether alcohol can cause problems with this medicine.

Interactions with foods

Grapefruit or grapefruit juice may change the level of gefitinib in your blood. Check with your doctor, nurse, or pharmacist about whether these or other foods may be a problem.

Tell all the doctors, dentists, nurses, and pharmacists you visit that you are taking this drug.

How is this drug taken or given?

Gefitinib is taken by mouth, as a 250 milligram (mg) tablet, once each day. It can be taken with or without food. It should be taken at about the same time each day. If you miss a dose, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not double your daily prescribed dose. Let your doctor know if you miss a dose.

Take this drug exactly as directed by your doctor. If you do not understand the instructions, ask your doctor or nurse to explain them to you. Store the medicine in a tightly closed container away from heat and moisture and out of the reach of children and pets.


A rash on the face, neck, and trunk is a common side effect, starting during the first 2 weeks of treatment and going away once treatment is stopped. Tell your doctor if it becomes severe or bothers you. Sunlight may make the rash worse. Wear sunscreen and hats, and limit your sun exposure while taking this drug.

This drug may cause diarrhea. If left unchecked, this could lead to dehydration and chemical imbalances in the body. Your doctor will likely prescribe medicine to help prevent or control this side effect. It is very important that you take this medicine as prescribed. Make sure you get the medicine right away, so that you will have it at home when you need it. Tell your doctor if the medicine doesn't stop the diarrhea.

Call your doctor if you have nausea, vomiting, or a poor appetite that doesn't get better.

Your doctor will likely test your blood throughout your treatment, looking for possible effects of the drug on blood counts or on blood chemistry levels. Based on the test results, you may be given medicines to help treat any effects. Your doctor may also need to reduce or delay your next dose of this drug, or even stop it altogether. Keep all your appointments for lab tests and doctor visits while taking this medicine.

Gefitinib may increase liver enzyme levels in your blood. Your doctor will likely check your liver function with blood tests on a regular basis. The drug may need to be stopped if the changes are severe. If you have liver metastasis or other liver problems before starting treatment, the doctor may need to monitor you more carefully.

In rare cases, patients have developed severe lung disease during treatment. Tell your doctor right away if you notice any possible symptoms of lung problems, such as shortness of breath or a new cough.

Gefitinib may affect the corneas in your eyes. Your doctor may suggest that you have a full eye exam by an eye doctor (ophthalmologist) before starting treatment. Tell your doctor right away if you notice eye irritation or vision changes.

Women should avoid pregnancy while taking this drug and for some time afterward. The drug may harm the fetus. Talk with your doctor about this.

Possible side effects

You will probably not have most of the following side effects, but if you have any talk to your doctor or nurse. They can help you understand the side effects and cope with them.


  • skin rash on face, neck, and trunk*
  • diarrhea*

Less common

  • acne
  • dry skin
  • itching
  • nausea
  • vomiting*
  • poor appetite*
  • abnormal blood tests which suggest that the drug is affecting the liver (Your doctor will discuss the importance of this finding, if any.)*


  • eye irritation*
  • damage to the lungs (might cause shortness of breath, cough, or fever)*
  • swelling in the hands or feet
  • mouth sores
  • allergic reaction, with symptoms like trouble breathing or swallowing, itching, hives, or shock
  • bleeding (nosebleeds, blood in the urine)
  • death due to lung damage or other cause

*See "Precautions" section for more detailed information.

There are some other side effects not listed above that can also occur in some patients. Tell your doctor or nurse if you develop these or any other problems.

FDA approval

Yes – first approved in 2003 (now approved for use only in people who have already been getting benefit from this drug).

Disclaimer: This information does not cover all possible uses, actions, precautions, side effects, or interactions. It is not intended as medical advice, and should not be relied upon as a substitute for talking with your doctor, who is familiar with your medical needs.

Last Medical Review: 02/26/2010
Last Revised: 02/26/2010