Gefitinib

What gefitinib is and how it works

Gefitinib is a prescription-only oral cancer medicine (an EGFR tyrosine kinase inhibitor) used to treat non-small cell lung cancer (NSCLC) in patients whose tumours have specific changes (mutations) in the EGFR gene. (1) (2)

You take gefitinib once a day as a tablet, exactly as your oncology team directs. Before starting, your tumour tissue is tested to confirm it has an EGFR mutation that gefitinib targets. It should only be prescribed and managed by a specialist experienced in treating lung cancer, because it carries serious risks including lung inflammation and liver problems, and requires regular monitoring.

Mechanism of action: how gefitinib works

Gefitinib is a small-molecule inhibitor of the epidermal growth factor receptor (EGFR) tyrosine kinase. By selectively inhibiting EGFR tyrosine kinase activity, gefitinib blocks downstream signalling pathways that drive proliferation and survival in EGFR-mutation-positive non-small cell lung cancer cells. (1) (2)

What gefitinib is used for

Before taking gefitinib

Do not take / not appropriate for

• Do not take gefitinib if you have had an allergic reaction to it or any of its ingredients. (all confirmed markets) (1)

Tell your clinician about

• Whether your tumour has been tested for an EGFR mutation, and the result -- gefitinib is only appropriate for EGFR-mutation-positive disease.
• Any history of lung disease or breathing problems.
• Any history of liver problems.
• Any history of stomach or bowel problems, including diverticular disease or peptic ulcers, since gastrointestinal perforation has been reported.
• Any history of severe or persistent diarrhoea.
• Any eye problems, including unusual eyelash growth, eye pain, or vision changes.
• Any skin conditions or history of severe skin reactions.
• All other medicines you take, especially those affecting stomach acid (proton pump inhibitors, H2 blockers, antacids), warfarin, or medicines that strongly affect CYP3A4.
• Pregnancy, plans for pregnancy, or breastfeeding -- and whether effective contraception is in place, since gefitinib may cause fetal harm.

How to take gefitinib

• Take gefitinib once daily, at approximately the same time each day, with or without food.
• Swallow the tablet whole with water; if you have difficulty swallowing, ask your care team about dispersing it in water first.
• If you vomit shortly after taking a dose, tell your care team -- do not automatically take a replacement dose without their guidance.
• If you miss a dose, take it as soon as you remember, unless it is less than 12 hours until your next scheduled dose -- in that case, skip the missed dose and resume your normal schedule; do not take two doses together.
• You will have regular clinical checks, including liver function tests and monitoring for new respiratory symptoms.
• Do not change your dose or stop taking gefitinib without talking to your oncology team first.

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)

Missed dose

If you miss a dose, take it as soon as you remember, unless it is less than 12 hours until your next scheduled dose -- in that case, skip the missed dose and take your next dose at the usual time. Do not take two doses together to make up for a missed one.

Overdose

Seek urgent medical attention if too much gefitinib may have been taken, or if you develop severe side effects such as severe diarrhoea, skin reactions, or liver problems. (1)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Serious warnings

Interactions

• Strong CYP3A4 inducers (such as rifampicin, phenytoin, carbamazepine, or St John's Wort) can reduce how well gefitinib works -- your clinician may increase your dose or choose an alternative if one of these cannot be avoided. (1) (2)
• Strong CYP3A4 inhibitors (such as ketoconazole, itraconazole, certain protease inhibitors, or clarithromycin) may increase gefitinib levels and side effects -- your clinician will monitor you closely. (1) (2)
• Medicines that raise stomach pH (proton pump inhibitors, H2-receptor blockers, and antacids) can reduce gefitinib absorption -- avoid if possible, or your clinician may advise on timing doses apart. (1) (2)
• Warfarin: gefitinib has been associated with increased INR and bleeding events -- your clinician will monitor your blood clotting tests more closely if you take both. (1) (2)
• Vinorelbine: combining with gefitinib may worsen low white blood cell counts (neutropenia). (2)

Pregnancy, breastfeeding, kidney/liver function, age

Monitoring

Before starting

• Confirmation of an EGFR-activating mutation in tumour tissue, using a robust and reliable test
• Baseline liver function tests
• Baseline respiratory status
• Pregnancy test and contraception plan where relevant
• Review of all other medicines, especially acid-reducing agents, warfarin, and strong CYP3A4 inhibitors/inducers

During treatment

• Periodic liver function tests.
• Monitoring for new or worsening respiratory symptoms (possible ILD).
• Monitoring for severe or persistent diarrhoea and signs of dehydration.
• Monitoring for eye symptoms and skin reactions.
• INR monitoring if taking warfarin concurrently.

Storage

Store at room temperature, away from moisture and light, out of reach of children.

Frequently asked questions

References

1. IRESSA (gefitinib) tablets, for oral use -- full prescribing information, revised 28 February 2023 (initial US approval 2015)U.S. Food and Drug Administration / National Library of Medicine DailyMed, full prescribing information · United States · accessed 2026-07-31 · source 1
2. Iressa 250 mg Film-Coated Tablets -- Summary of Product Characteristics (emc product 6602)UK Medicines and Healthcare products Regulatory Agency / electronic medicines compendium (emc), Summary of Product Characteristics · United Kingdom · accessed 2026-07-31 · source 2
3. IRESSA (gefitinib) -- Product Monograph (most recently confirmed revision 27 September 2012)Health Canada -- AstraZeneca Canada Inc., product monograph · Canada · accessed 2026-07-31 · source 3
4. IRESSA (gefitinib) 250 mg tablet blister pack -- ARTG registration 90010; generic GEFTIRESS (Cipla) and gefitinib (Apotex) also ARTG-registeredAustralian Therapeutic Goods Administration (TGA), Australian Register of Therapeutic Goods (ARTG) · Australia · accessed 2026-07-31 · source 4
5. IRESSA (gefitinib) 250 mg tablets -- New Zealand Data SheetNew Zealand Medicines and Medical Devices Safety Authority (Medsafe) · New Zealand · accessed 2026-07-31 · source 5
6. Iressa (gefitinib) -- European Public Assessment Report (EPAR), EU centralised marketing authorisation EMEA/H/C/001016, granted 24 June 2009European Medicines Agency (EMA) · European Union · accessed 2026-07-31 · source 6

Brand names by country

Single-ingredient gefitinib names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries