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Gefinitib (Iressa®)

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About This Drug

Gefitinib is used to treat cancer. It is given orally (by mouth)

Possible Side Effects

  • Skin reactions such as rashes, dry skin, rash with fluid-filled bumps/blisters
  • Diarrhea (loose bowel movements)

Note: Each of the side effects above was reported in 20% or greater of patients treated with gefitinib. Not all possible side effects are included above.

Warnings and Precautions

  • Scarring of the lungs that causes stiffness in the lungs and/or inflammation (swelling) of the lungs, which makes breathing difficult and can be life-threatening.
  • Changes in your liver function, which can cause liver failure and be life-threatening.
  • Severe diarrhea.
  • Perforation - an abnormal hole in your stomach, small and/or large intestine.
  • Blurred vision or other changes in eyesight.
  • Severe allergic skin reactions. You may develop blisters on your skin that are filled with fluid or a severe red rash all over your body that may be painful. Skin can sometimes be weeping or peeling off.

Note: Some of the side effects above are very rare. If you have concerns and/or questions, please discuss them with your medical team.

How to Take Your Medication

  • You can take the medicine with or without food.
  • If you have difficulties swallowing tablets whole, you can dissolve tablets in 4 to 8 oz. of water and stir for 15 min, immediately drink the solution. Rinse the glass with 4 to 8 oz. and drink immediately again.
  • If you take a proton pump inhibitor antacids such as (Protonix®, Nexium®, Prilosec®), take this drug at least 12 hours before or 12 hours after you take the antacid. If you take H2 receptor blocker antacids such as (Pepcid®, Tagamet®, and Zantac®), take this drug at least 6 hours before or 6 hours after you take the antacid. Talk with your doctor to determine the best time to take gefitinib with these medications.
  • Missed dose: If you miss a dose, take it as soon as you think about it, unless it is within 12 hours of your next dose, then skip the missed dose and go back to your normal schedule. Do not take 2 doses at the same time or extra doses.
  • Handling: Wash your hands after handling your medicine, your caretakers should not handle your medicine with bare hands and should wear latex gloves.
  • This drug may be present in the saliva, tears, sweat, urine, stool, vomit, semen, and vaginal secretions. Talk to your doctor and/or your nurse about the necessary precautions to take during this time.
  • Storage: Store this medicine in the original container at room temperature.
  • Disposal of unused medicine: Do not flush any expired and/or unused medicine down the toilet or drain unless you are specifically instructed to do so on the medication label. Some facilities have take-back programs and/or other options. If you do not have a take-back program in your area, then please discuss with your nurse or your doctor how to dispose of unused medicine.

Treating Side Effects

  • Drink plenty of fluids (a minimum of eight glasses per day is recommended).
  • If you have loose bowel movements, you should drink more fluids so that you do not become dehydrated (lack water in the body from losing too much fluid).
  • If you have diarrhea, eat low-fiber foods that are high in protein and calories and avoid foods that can irritate your digestive tracts or lead to cramping.
  • Ask your nurse or doctor about medicine that can lessen or stop your diarrhea.
  • Moisturize your skin several times day.
  • Avoid sun exposure and apply sunscreen routinely when outdoors.
  • If you get a rash do not put anything on it unless your doctor or nurse says you may. Keep the area around the rash clean and dry. Ask your doctor for medicine if your rash bothers you.

Food and Drug Interactions

  • This drug may interact with grapefruit and grapefruit juice. Talk to your doctor as this could make side effects worse.
  • Check with your doctor or pharmacist about all other prescription or over-the-counter medicines and dietary supplements (vitamins, minerals, herbs or others) you are taking before starting this medicine as there are known drug interactions with gefinitib. Also, check with your doctor or pharmacist before starting any new prescription, over-the-counter medicines, or dietary supplements to make sure that there are no interactions.
  • Avoid the use of St. John’s Wort while taking gefitinib as this may lower the levels of the drug in your body, which can make it less effective.
  • There are known interactions of gefinitib with blood-thinning medicine such as warfarin. Ask your doctor what precautions you should take.
  • Drugs that treat heartburn and stomach upset such as Protonix®, Nexium®, Prilosec®, Pepcid®Tagamet®, and Zantac® may lower the effect of your cancer treatment if taken with gefitinib. Follow the instructions in the How to Take Your Medication section, or talk to your doctor.

When to Call the Doctor

Call your doctor or nurse if you have any of these symptoms and/or any new or unusual symptoms:

  • Fever of 100.4 F (38 C) or higher
  • Chills
  • Blurred vision or other changes in eyesight
  • Sensitivity to light
  • Pain in your chest
  • Dry cough
  • Trouble breathing
  • Severe abdominal pain that does not go away
  • Nausea that stops you from eating or drinking and/or is not relieved by prescribed medicine
  • Throwing up more than 3 times a day
  • Diarrhea, 4 times in one day or diarrhea with lack of strength or a feeling of being dizzy
  • Flu-like symptoms: fever, headache, muscle and joint aches, and fatigue (low energy, feeling weak)
  • A new rash or itching that is not relieved by prescribed medicines
  • Signs of possible liver problems: dark urine, pale bowel movements, bad stomach pain, feeling very tired and weak, unusual itching, or yellowing of the eyes or skin
  • If you think you may be pregnant

Reproduction Warnings

  • Pregnancy warning: This drug can have harmful effects on the unborn baby. Women of childbearing potential should use effective methods of birth control during your cancer treatment and for at least 2 weeks after treatment. Let your doctor know right away if you think you may be pregnant.
  • Breastfeeding warning: Women should not breastfeed during treatment because this drug could enter the breast milk and cause harm to a breastfeeding baby.
  • Fertility warning: In women, this drug may affect your ability to have children in the future. Talk with your doctor or nurse if you plan to have children. Ask for information on egg banking.

Revised June 2019

This patient information was developed by Via Oncology, LLC © 2019. This information is not intended to be used as a substitute for professional medical advice, diagnosis, or treatment. You should not rely entirely on this information for your health care needs. Ask your own doctor or health care provider any specific medical questions that you have. 

CLIENT acknowledges that the Via Pathways and Via Portal are information management tools only, and that Via Oncology, LLC has not represented the Via Pathways or Via Portal as having the ability to diagnose disease, prescribe treatment, or perform any other tasks that constitute the practice of medicine. The clinical information contained in the Via Pathways and Via Portal are intended as a supplement to, and not a substitute for, the knowledge, expertise, skill, and judgment of physicians, pharmacists and other healthcare professionals involved with patient care at CLIENT facilities.