See also Warning section.
Diarrhea, rash, acne, nausea, vomiting, loss of appetite, nail problems, hair loss, red/sore mouth or throat, or unusual weakness may occur. If any of these effects persist or worsen, notify your doctor or pharmacist right away.
Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.
Persistent nausea, vomiting, diarrhea, or loss of appetite may result in a serious loss of body water (dehydration) and kidney problems. Contact your doctor promptly if you notice any symptoms of dehydration, such as: unusual decreased urination, unusual dry mouth/thirst, fast heartbeat, dizziness/lightheadedness.
Tell your doctor right away if any of these unlikely but serious side effects occur: unusual bleeding (coughing up blood, blood in urine), eye irritation/pain, swelling of the ankles/feet.
Gefitinib may cause rare (possibly fatal) lung disease (interstitial lung disease-ILD). Tell your doctor right away if you develop trouble breathing, cough or fever.
If you have persistent diarrhea or skin rashes contact your doctor. Your doctor may temporarily stop gefitinib (for up to 14 days) which may help reverse those side effects. Treatment is then resumed with the same dosage.
An allergic reaction to this drug is unlikely, but seek immediate medical attention if it occurs. Symptoms of an allergic reaction include: severe rash, itching/swelling (especially of the face/tongue/throat), dizziness, trouble breathing.
This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.
In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.
In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.