Iressa (gefitinib) is a targeted therapy used to treat non-small cell lung cancer (NSCLC) that carries a specific mutation in the EGFR (epidermal growth factor receptor) gene. It blocks the mutated EGFR signal that drives cancer cell growth and division.

Testing for EGFR mutations is essential before starting treatment, as Iressa is only effective in mutation-positive tumours.

Take one 250 mg tablet once daily, with or without food. Take it at the same time each day.

If you have difficulty swallowing tablets, dissolve the tablet in half a glass of water without crushing it. Stir until dispersed, drink immediately, and rinse the glass with water to get the full dose.

If you remember within 12 hours of the usual time, take it as soon as possible. If more than 12 hours have passed, skip the missed dose and take the next one as usual. Never take two doses at once.

Contact your oncologist or emergency department immediately.

• Store below 30°C
• Keep in the original packaging
• Keep out of reach of children

Very common side effects:

• Diarrhoea: often mild to moderate. Drink plenty of fluids and tell your doctor if it is severe or persistent
• Skin rash and acne-like skin changes: a common effect that often indicates the medicine is working
• Nausea
• Dry skin and mouth
• Nail changes and nail infections
• Elevated liver enzymes

Serious side effects:

• Interstitial lung disease (ILD): new or worsening cough, breathlessness, or fever should be reported immediately. If ILD is confirmed, Iressa must be stopped
• Hepatotoxicity: severe liver enzyme elevations may require dose adjustment or stopping
• Eye problems (keratitis): persistent eye irritation or pain requires urgent assessment

Regular blood tests for liver function are required during treatment.

• Strong CYP3A4 inducers (rifampicin, phenytoin, carbamazepine, St John's Wort): significantly reduce gefitinib levels
• Warfarin: gefitinib may increase INR. Monitor more frequently
• Medicines that raise stomach pH (PPIs, H2 blockers, antacids): may reduce gefitinib absorption

Tell your oncologist and pharmacist about all medicines you take.

Why does the skin rash mean the medicine might be working?

EGFR is active not only in lung cancer cells but also in normal skin cells. When gefitinib blocks EGFR in the skin, it can cause a characteristic acne-like rash. Studies have found that patients who develop a noticeable skin rash tend to have better treatment outcomes. This is not an allergy but a pharmacological effect. Your doctor can prescribe treatments to manage symptoms if needed.

How long will I take Iressa?

Iressa is taken continuously until the cancer progresses or side effects become unacceptable. In some patients, it can control the disease for many months or years. Eventually, most tumours develop resistance, at which point your oncologist will discuss next steps.

Ace provides accurate and independent information medically reviewed on prescription medications. This material is provided for educational purposes only and is not intended for medical advice, diagnosis or treatment.