EGFR tyrosine-kinase inhibitor Pregnancy: Gefitinib should not be used during pregnancy unless clearly necessary — there are no data in pregnant women and animal studies have shown reproductive toxicity. Women of childbearing potential must be advised not to become pregnant during therapy. Contraindicated during breast-feeding, which must be discontinued while receiving gefitinib.

Gefitinib (Specialist drug)

Brand names: Iressa

Gefitinib is an oral epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor used as first-line treatment of locally advanced or metastatic non-small-cell lung cancer with activating EGFR mutations.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 250 mg (one tablet)

Route: Oral — may be taken with or without food. Swallow whole with water; if swallowing whole tablets is not possible the tablet may be dispersed (uncrushed) in half a glass of non-carbonated drinking water, swirling occasionally until dispersed (up to 20 minutes), drunk immediately (within 60 minutes), then the glass rinsed with half a glass of water which is also drunk. The dispersion can also be given through a naso-gastric or gastrostomy tube. No other liquids should be used.

Frequency: Once daily, at about the same time each day

INDICATION: locally advanced or metastatic NSCLC — EGFR mutation assessment of tumour tissue (or circulating tumour DNA from a plasma sample if tissue is not evaluable) should be attempted for all patients. Treatment should be initiated and supervised by a physician experienced in the use of anticancer therapies. MISSED DOSE: take as soon as remembered, but if less than 12 hours to the next dose the missed dose should not be taken; never take a double dose. TOXICITY: patients with poorly tolerated diarrhoea or skin reactions may be managed by a brief therapy interruption (up to 14 days) followed by reinstatement of the 250 mg dose; if treatment cannot be tolerated after an interruption, discontinue and consider an alternative. HEPATIC: patients with moderate to severe hepatic impairment (Child-Pugh B or C) due to cirrhosis have increased plasma gefitinib concentrations and should be closely monitored for adverse events. ELDERLY: no dose adjustment on the basis of age. CYP2D6 POOR METABOLISERS: no specific dose adjustment recommended, but monitor closely for adverse events. PAEDIATRIC: safety and efficacy in children and adolescents under 18 years have not been established, and there is no relevant use in the paediatric population for NSCLC. US LABELLING (cross-check, not in the UK SPC extract): increase gefitinib to 500 mg daily in patients receiving a strong CYP3A4 inducer, and resume 250 mg seven days after the inducer is discontinued.

Dose adjustments

Renal

No dose adjustment is required at creatinine clearance greater than 20 mL/min. Only limited data are available at creatinine clearance 20 mL/min or less and caution is advised in these patients.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients
Breast-feeding

Side effects

Diarrhoea — very common, mainly mild or moderate (CTC grade 1 or 2)
Skin reactions — very common; mainly a mild or moderate pustular rash, sometimes itchy, with dry skin including skin fissures (rash, acne, dry skin and pruritus occur in more than 20% of patients)
Nausea, vomiting and stomatitis — very common, mainly mild to moderate; anorexia very common
Elevations in alanine aminotransferase — very common (AST and total bilirubin elevations common; hepatitis uncommon, with isolated reports of hepatic failure, some fatal)
Interstitial lung disease — occurred in 1.3% of patients, often severe (CTC grade 3-4), with fatal outcomes reported

Interactions

CYP3A4 inducers (e.g. phenytoin, carbamazepine) — may increase the metabolism of gefitinib and decrease gefitinib plasma concentrations (UK SPC section 4.4; the full section 4.5 was not retrieved in this bundle)
Strong CYP3A4 inducers (e.g. rifampicin, phenytoin) — US labelling directs increasing gefitinib to 500 mg daily during use and resuming 250 mg 7 days after the inducer is stopped
Strong CYP3A4 inhibitors (e.g. ketoconazole, itraconazole) — decrease gefitinib metabolism and increase gefitinib plasma concentrations; monitor for adverse reactions (US labelling)
Drugs that elevate gastric pH (proton pump inhibitors, H2-receptor antagonists, antacids) — may reduce plasma concentrations of gefitinib; avoid concomitant proton pump inhibitors if possible (US labelling)
Warfarin — haemorrhage reported; monitor prothrombin time or INR (US labelling)

Clinical monograph

How it works

It reversibly inhibits the tyrosine kinase activity of EGFR, blocking downstream proliferative and survival signalling in EGFR mutation-positive tumours.

Prescribing in practice

Interstitial lung disease can occur and may be fatal; withhold and investigate promptly if new or worsening breathlessness, cough or fever develops.
Use should be limited to tumours with confirmed activating EGFR mutations, under specialist oncology supervision.
Hepatotoxicity, diarrhoea and skin reactions are common, and concurrent CYP3A4 inducers or drugs raising gastric pH can reduce exposure.

Monitoring

Monitor liver function periodically and review for pulmonary symptoms throughout treatment.

Counselling the patient

Report new or worsening breathlessness, cough or fever urgently.
Tell the team about rash, persistent diarrhoea or eye symptoms.
Disclose all other medicines, including antacids and acid-suppressing treatment.

Evidence & guidelines

First-line benefit in EGFR mutation-positive NSCLC was established in the IPASS randomised controlled trial.

Reference: NICE TA192; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways