Iressa (Gefitinib)

• Gefitinib targets the EGFR pathway and is used in the management of EGFR‑mutated non‑small cell lung cancer.
• First‑line therapy for EGFR‑mutated NSCLC: provides targeted inhibition of tumor growth.
• Second‑line therapy after chemotherapy for EGFR‑mutated NSCLC: offers an alternative targeted option.
• Maintenance therapy in EGFR‑mutated NSCLC: helps sustain disease control after initial response.

• Gefitinib selectively binds to the intracellular ATP‑binding site of the epidermal growth factor receptor (EGFR) tyrosine kinase, preventing autophosphorylation and downstream signaling through the MAPK, PI3K/AKT and STAT pathways. This blockade reduces cellular proliferation, angiogenesis, and survival signals in tumor cells that rely on EGFR activation.

Gefitinib may cause a range of adverse reactions that vary in frequency and severity.

Common Side Effects

• Diarrhea: mild to moderate watery stools.
• Skin rash: erythematous papular eruption, often on the face and trunk.
• Nausea: occasional upset stomach.
• Vomiting: intermittent episodes.
• Decreased appetite: reduced food intake.
• Fatigue: general tiredness.

Serious or Rare Side Effects

• Interstitial lung disease: new or worsening respiratory symptoms.
• Hepatotoxicity: elevated liver enzymes or jaundice.
• Severe skin reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• QT interval prolongation: potential cardiac arrhythmia.
• Ocular toxicity: visual disturbances or corneal changes.
• Severe hepatic failure: signs of liver dysfunction.

• Before initiating Gefitinib, clinicians should assess patient‑specific risk factors and monitor for known safety concerns.
• Renal function: evaluate baseline creatinine clearance.
• Hepatic function: monitor liver enzymes regularly.
• Skin reactions: inspect for severe rash or desquamation.
• Pulmonary symptoms: watch for cough, dyspnea, or new infiltrates.
• Drug interactions: review concomitant medications for CYP3A4 modulators.
• Store at ambient temperature: keep in the original pack, protect from moisture and direct sunlight.

Gefitinib's pharmacokinetics can be altered by co‑administered drugs that affect CYP3A4 activity.

Major Interactions (Avoid)

• Rifampin, carbamazepine, phenytoin: strong CYP3A4 inducers that may markedly reduce gefitinib exposure.
• St. John’s wort: herbal CYP3A4 inducer that can lower drug levels.
• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may increase gefitinib concentrations and risk of toxicity.

Moderate Interactions (Monitor Closely)

• Warfarin: may enhance anticoagulant effect, requiring INR monitoring.
• Simvastatin: increased risk of myopathy when combined.
• Systemic corticosteroids: may heighten the incidence of skin reactions.