Gefitinib

What is Gefitinib?

Gefitinib is a prescription cancer medicine. It belongs to a drug class called EGFR tyrosine kinase inhibitors (TKIs), a type of targeted therapy. It was first sold under the brand name Iressa, and generic versions are also available.

Approved use: Gefitinib is approved in the United States for adults with metastatic non-small cell lung cancer (NSCLC) whose tumors have certain changes (mutations) in the EGFR gene. These are called exon 19 deletions or exon 21 (L858R) substitution mutations. An FDA-approved test must confirm the mutation before treatment.

Formulation and strength: Gefitinib is taken by mouth as a 250 mg film-coated tablet. Other uses, such as use in different cancer types, should be discussed only with your oncologist.

What is the Recommended Dosage of Gefitinib?

Your dose is set by your oncologist and should always follow their instructions and your pharmacy label. In general, gefitinib is a tablet taken by mouth, with or without food, on a schedule your specialist gives you.

Your care team may adjust the dose or schedule based on:

• Your condition and tolerance: Treatment may be paused or changed if side effects occur.
• Liver function: Blood tests may lead to changes if liver problems develop.
• Other medicines: Some drugs change how much gefitinib is in your body.
• Overall health: Age and other conditions can matter.

Do not change, skip, or stop doses on your own. If you have trouble swallowing tablets, ask your care team or pharmacist for approved options instead of crushing or splitting the tablets yourself.

How Gefitinib Works

Some lung cancer cells have changes in the EGFR gene. These changes can keep a protein on the cell surface “switched on,” sending constant signals telling the cancer cell to grow and divide.

Gefitinib blocks the tyrosine kinase part of that protein, which reduces those growth signals. In patients whose tumors have these specific mutations, this can slow tumor growth or shrink tumors. Gefitinib is used to control the disease, and it is not considered a cure. Over time, cancer cells can become resistant, which is why regular scans and follow-up visits are important.

Is a Prescription Required to Buy Gefitinib Online?

Yes. Gefitinib is prescription-only. It should be prescribed and monitored by a licensed medical oncologist (a cancer specialist), sometimes working with a pulmonologist or thoracic oncology team.

• Genetic testing of the tumor is needed to confirm that the medicine fits the cancer type.
• Buy only from a licensed pharmacy that requires a valid prescription.
• Counterfeit or substandard cancer medicines exist. Be cautious of websites that sell without a prescription or ship from unclear sources.
• Check that the tablets match what your pharmacist describes, and ask your pharmacist if packaging or appearance looks different.

Side Effects of Gefitinib

Not everyone gets every side effect. Many can be managed with help from your care team.

Common Side Effects

• Diarrhea
• Skin rash, acne-like rash, dry or itchy skin
• Nausea, vomiting, or loss of appetite
• Mouth sores (stomatitis)
• Tiredness
• Eye redness or irritation (conjunctivitis)
• Abnormal liver blood tests, which are usually found through lab monitoring

Serious Side Effects

These are uncommon but need prompt attention:

• Lung problems (interstitial lung disease): new or worsening shortness of breath, cough, or fever
• Liver problems: yellowing of the skin or eyes, dark urine, severe stomach pain, or unusual tiredness
• Severe or persistent diarrhea that leads to dehydration
• Severe stomach or belly pain (rarely, a tear in the stomach or intestine)
• Serious eye problems: eye pain, vision changes, or severe redness
• Severe skin reactions: blistering, peeling skin, or mouth sores with skin symptoms

Seek immediate medical care if you have trouble breathing, signs of liver injury, severe belly pain, severe blistering skin reactions, or sudden vision changes. Contact your oncology team promptly for diarrhea that does not improve or a worsening rash.

Drug Interactions

Tell your oncologist and pharmacist about everything you take, including prescription drugs, over-the-counter (OTC) products, vitamins, supplements, and herbal products. Major categories include:

• Strong CYP3A4 inducers (such as rifampin, phenytoin, carbamazepine) can lower gefitinib levels and may make it less effective.
• Strong CYP3A4 inhibitors (such as itraconazole and ketoconazole) can raise gefitinib levels and may increase side effects.
• Acid-reducing medicines, including proton pump inhibitors, H2 blockers, and antacids, can reduce how well gefitinib is absorbed. Timing and choice of these products should be directed by your care team.
• Warfarin and other blood thinners: Bleeding risk or INR changes have been reported, so closer monitoring may be needed.
• Medicines processed by CYP2D6 (such as some heart rhythm and mood medicines) may be affected.
• Herbal products, especially St. John’s wort, can lower gefitinib levels. Grapefruit products may also affect some medicines, so ask your pharmacist.

Bring a complete, updated medication list to every appointment.

Safety & Important Considerations

• Liver disease: Liver blood tests are checked before and during treatment. Dose changes or stopping the drug may be needed if problems arise.
• Kidney disease: Little change is expected for mild to moderate kidney impairment. Discuss severe kidney disease with your specialist.
• Pregnancy: Gefitinib can harm an unborn baby. Effective contraception is advised during treatment and for a period after the last dose (at least two weeks according to U.S. labeling). Tell your oncologist right away if you are or may become pregnant.
• Breastfeeding: Breastfeeding is not recommended during treatment and for a period after the last dose.
• Older adults and children: Gefitinib is approved for adults. Safety and effectiveness in children have not been established. Older adults are monitored in the same way, with attention to overall health.
• Monitoring: Expect regular visits, imaging scans, and blood tests (including liver function). Report new breathing symptoms, eye symptoms, or severe skin or digestive problems.
• Sun and skin care: Gentle skin care and sun protection can help with rash, but follow your care team’s specific advice.

Who This Medication Is For

Gefitinib is intended for adults with metastatic NSCLC whose tumors have confirmed EGFR exon 19 deletions or exon 21 L858R mutations. It is not appropriate for lung cancers without these changes, and tumor testing is how specialists decide whether it fits. Treatment plans differ from person to person.

Who Should Not Take Gefitinib

U.S. labeling does not list formal contraindications, but gefitinib is not suitable for everyone, and some people need extra caution. In some other countries, severe allergy to gefitinib or its ingredients and breastfeeding are listed as reasons not to use it.

Discuss with your oncologist before starting if you:

• Have had an allergic reaction to gefitinib or any tablet ingredient
• Have lung disease, a history of lung inflammation, or breathing problems
• Have liver disease
• Have eye problems or wear contact lenses
• Are pregnant, planning pregnancy, or breastfeeding
• Have a history of stomach or bowel problems, including ulcers
• Take medicines that interact with gefitinib

What to Do If You Miss a Dose

• Take the missed dose as soon as you remember, unless your next dose is due within about 12 hours. In that case, skip the missed dose.
• Never take two doses at once to make up for a missed one.
• If you are unsure what to do, or you miss several doses, contact your oncology team or pharmacist.

Related Medications to Gefitinib

Other EGFR-targeted tablets are used for EGFR-mutated NSCLC, including erlotinib, afatinib, dacomitinib, and osimertinib. Other approaches, such as chemotherapy, immunotherapy, radiation, or combination plans, may be considered depending on the cancer’s features and your health. These medicines differ in side effects, interactions, and approved uses. Switching or combining treatments must be decided together with your oncologist.

Storage Instructions

• Store at room temperature, about 68°F to 77°F (20°C to 25°C), with brief trips between 59°F and 86°F (15°C to 30°C) allowed.
• Keep tablets in the original container with the lid tightly closed, away from moisture (not in the bathroom) and light.
• Keep out of reach of children and pets.
• Do not use tablets past the expiration date. Ask your pharmacist about safe disposal of unused medicine.
• Caregivers handling the tablets should wash their hands afterward, and pregnant caregivers should ask the care team about handling precautions.

Disclaimer:This page is for educational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Patients must consult a licensed medical oncologist before starting, changing, or stopping treatment. Treatment decisions must be based on a full clinical evaluation by a qualified specialist.