GEFITINIB
About Gefitinib
Gefitinib — first-generation EGFR tyrosine kinase inhibitor
Gefitinib is an oral targeted medicine for non-small cell lung cancer with an activating EGFR mutation. It was among the first EGFR inhibitors licensed and remains in use where it is appropriate.
How Gefitinib works
It competes with ATP at the tyrosine kinase domain of the epidermal growth factor receptor, blocking the signal that drives proliferation in EGFR-mutated tumours. Binding is reversible, unlike the later irreversible inhibitors, and it does not overcome the T790M resistance mutation — which is why resistance testing follows progression.
What it is licensed for
Locally advanced or metastatic non-small cell lung cancer with activating mutations of the EGFR tyrosine kinase.
How it is taken
An oral tablet taken once daily, with or without food. Dosage must be determined by a qualified healthcare provider.
What your prescriber monitors
Liver function tests; skin and gastrointestinal effects, which are common with this class; and any new respiratory symptoms. Ophthalmic assessment is arranged for persistent eye irritation, since corneal changes and aberrant eyelash growth are described. Weight and hydration are followed where diarrhoea is troublesome, and electrolytes checked if it persists.
Important cautions and interactions
Rash and diarrhoea are frequent and are managed actively rather than tolerated silently. Interstitial lung disease is uncommon but serious. Liver enzyme rises occur and are monitored. Medicines that raise stomach pH, including proton pump inhibitors, reduce absorption. Strong CYP3A4 inducers lower blood levels. Smoking accelerates clearance of this medicine, so smoking status is recorded and cessation support offered where relevant.
Where Gefitinib sits in its class
Gefitinib and erlotinib are the first-generation, reversible EGFR inhibitors; afatinib and dacomitinib bind irreversibly, and osimertinib was designed to remain effective once the T790M resistance mutation appears. Gefitinib's absorption depends on stomach acid in a way the later agents do not, which is a practical difference that matters day to day rather than a theoretical one.
What to expect in the first weeks
An acne-like rash on the face, scalp and upper trunk commonly emerges in the first two to three weeks and responds better to early moisturiser, sun protection and prescribed topical or oral treatment than to waiting. Diarrhoea often starts in the same window and is managed actively. Liver enzymes are checked in the first month or two. Sudden breathlessness or fever requires same-day assessment.
Before you start Gefitinib
List anything you take for reflux or indigestion, including over-the-counter antacids and proton pump inhibitors, because they reduce how much gefitinib is absorbed. Bring your tumour's EGFR mutation report. Mention any liver problem, any existing lung disease, and any skin condition, and ask what to use for the rash before it appears rather than after.
Generic Gefitinib and Iressa
Generic Gefitinib contains the same active ingredient as Iressa®, produced by licensed pharmaceutical manufacturers. The brand name and the price differ, not the molecule.
Read our full guide: Generic Iressa (Gefitinib)
Gefitinib is a prescription-only medicine. A valid prescription is required and every order is reviewed by a licensed pharmacist before dispatch. Used as prescribed by a licensed medical professional.
Frequently asked questions
How does gefitinib differ from osimertinib?
Both block mutated EGFR, but gefitinib binds reversibly and is a first-generation inhibitor, while osimertinib binds irreversibly and was designed to remain effective against the T790M resistance mutation. Which is appropriate depends on the tumour's mutation profile and treatment history — a decision for your oncologist.
Do indigestion medicines affect gefitinib?
Yes. Gefitinib absorption depends on stomach acidity, so proton pump inhibitors and other acid-reducing medicines can lower how much reaches the bloodstream. Tell your prescriber about anything you take for reflux or indigestion, including over-the-counter products.
Is the rash from gefitinib a reason to stop?
Skin reactions are common with EGFR inhibitors and are usually managed with topical treatment and dose adjustment rather than by stopping. Report it so it can be treated — do not stop on your own.
Do I need a prescription to order Gefitinib?
Yes. Gefitinib is a prescription-only medicine. Upload a valid prescription at checkout — every order is reviewed by a licensed pharmacist before dispatch.
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Last updated: October 3, 2026
Medically reviewed by
A. Srinivasan
A. Srinivasan is a licensed clinical pharmacist with 24 years of experience. He holds a B.Pharm and M.Pharm from University of Madras. At OnlineMeds, he reviews medicine and health content to help ensure it is accurate, evidence-based, and easy to understand.