Iressa (Gefitinib)

Gefitinib is used in the management of EGFR‑driven non‑small cell lung cancer, targeting tumors with specific genetic alterations.

• Non‑small cell lung cancer (EGFR activating mutations): improves progression‑free survival by inhibiting tumor cell growth.
• Metastatic NSCLC after prior chemotherapy: offers a targeted oral option when conventional chemotherapy has failed.
• First‑line therapy for EGFR‑mutated NSCLC: provides an alternative to chemotherapy as initial treatment in eligible patients.
• Recurrent EGFR‑mutated NSCLC: delays disease progression in patients with disease recurrence.

• Gefitinib selectively binds to the adenosine triphosphate (ATP)‑binding pocket of the epidermal growth factor receptor (EGFR) tyrosine kinase. By blocking ATP access, it prevents autophosphorylation of the receptor and downstream signaling through the MAPK, PI3K/AKT and STAT pathways, which are essential for tumor cell proliferation, survival and angiogenesis. The blockade leads to cell‑cycle arrest and apoptosis in mutant tumor cells.

Gefitinib may cause a range of adverse reactions, which are categorized by frequency and severity.

Common Side Effects

• Diarrhea: mild to moderate watery stools.
• Rash: acne‑like skin eruption, often on the face and trunk.
• Nausea: occasional feeling of stomach upset.
• Elevated liver enzymes: mild increases in ALT/AST.
• Fatigue: persistent tiredness.
• Anorexia: loss of appetite.

Serious or Rare Side Effects

• Interstitial lung disease: potentially life‑threatening pulmonary inflammation.
• Severe hepatotoxicity: marked elevation of liver enzymes or liver failure.
• Cardiac arrhythmias: QT interval prolongation leading to rhythm disturbances.

When prescribing Gefitinib, clinicians should consider several precautionary measures to minimize risk and ensure safe use.

• Pregnancy: contraindicated; avoid use in pregnant women due to fetal toxicity.
• Breastfeeding: not recommended; drug may be excreted in milk.
• Hepatic impairment: assess liver function before initiation and monitor regularly.
• Renal impairment: dose adjustment may be required in severe kidney dysfunction.
• Cardiac monitoring: obtain baseline ECG and monitor QT interval during therapy.
• Store at ambient temperature: keep tablets below 25 °C in the original container, protected from moisture and light.

Gefitinib can interact with other medicines, altering its plasma concentration or increasing toxicity.

Major Interactions (Avoid)

• Strong CYP3A4 inducers (e.g., rifampicin, carbamazepine): markedly reduce gefitinib exposure.
• Antacids containing aluminum or magnesium: decrease absorption if taken simultaneously.

Moderate Interactions (Monitor Closely)

• CYP3A4 inhibitors (e.g., ketoconazole, erythromycin): may increase gefitinib levels.
• Warfarin: enhanced anticoagulant effect, monitor INR.
• Proton pump inhibitors: may modestly reduce gefitinib absorption; consider timing separation.
• St. John’s wort: potential reduction in efficacy; advise against concurrent use.