Gefitinib
Kinase inhibitors (targeted oncology)
Kinase inhibitors (targeted oncology)High alert
An error with this medicine can cause serious harm: double checks and protocols are used.
A first-generation, reversible EGFR kinase inhibitor for lung cancer with EGFR exon 19 deletion or L858R mutation; typical effects are rash and diarrhoea.
Quick facts
- Group
- Kinase inhibitors (targeted oncology)
- Target
- EGFR tyrosine kinase domain
- Used for
- First-line treatment
- Key effects
- Acne-like rash · Diarrhoea · Nausea
- Monitor
- EGFR mutation test before starting · New cough
- ATC
- L01EB01
No doses: the clinician sets them by the current guideline.
Mechanism of action
The crystal shows gefitinib in the ATP pocket of the human EGFR kinase domain.
Gefitinib competes with ATP and reversibly inhibits the EGFR tyrosine kinase, blocking receptor autophosphorylation and downstream signalling. It binds the activating mutations (exon 19 deletion, L858R) more tightly than the normal receptor, so EGFR-mutant lung cancers respond; resistance usually comes from the T790M mutation.
- Competes with ATP in the EGFR kinase
- Autophosphorylation is blocked (reversibly)
- Downstream growth signals stop
- Works in exon 19 deletion or L858R tumours
Indications
- First-line treatment of metastatic non-small cell lung cancer with EGFR exon 19 deletion or exon 21 L858R mutation. Lung cancer →
Adverse effects
Common
- Acne-like rash, dry skin
- Diarrhoea
- Nausea, loss of appetite
- Raised liver enzymes
Contraindications
- No absolute contraindications in the label
Key interactions
- Strong CYP3A4 inducers
- Lower gefitinib levels.
- CYP3A4 inhibitors
- Raise gefitinib levels; the patient is watched for adverse effects.
- Proton pump inhibitors
- Raise gastric pH and reduce absorption; avoided if possible.
- Warfarin
- Bleeding and raised INR; INR is monitored.
What is monitored
- EGFR mutation test before starting
- Liver tests periodically
- New cough, breathlessness or fever
- Diarrhoea, skin and eyes
- INR if on warfarin
Administration and safety
- Oral; swallowed whole at about the same time each day.
- Check the name carefully: kinase inhibitors with similar «-tinib» names are not interchangeable.
- Proton pump inhibitors are avoided if possible.
Pregnancy and breastfeeding
Can harm the fetus; effective contraception is used and breastfeeding is stopped.
Nursing care
- Ask about breathlessness, cough and fever at each visit; sudden symptoms are reported at once.
- Review liver test results.
- Teaching: skin care and sun protection, report severe diarrhoea or eye pain, and use contraception.
Pharmacokinetics
- Absorption
- Oral; with or without food; high gastric pH reduces absorption.
- Distribution
- Very wide tissue distribution.
- Metabolism
- Liver, mainly CYP3A4; CYP2D6 forms a metabolite, and CYP2D6 poor metabolisers have higher levels.
- Elimination
- Mainly in the faeces.
- Half-life
- About two days.
Test yourself
Think of the answer, then tap the question to see it.
Which patients with lung cancer benefit from gefitinib?
Those whose tumours carry EGFR exon 19 deletion or exon 21 L858R mutation.
Which serious lung adverse effect requires stopping gefitinib?
Interstitial lung disease.
Which genetic group of patients has higher gefitinib exposure?
CYP2D6 poor metabolisers.
Connections
← Back to the class: Kinase inhibitors (targeted oncology)
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - GEFITINIB tablet, film coated (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.