Iressa (Gefitinib)

Gefitinib targets EGFR‑driven non‑small cell lung cancer, an oncologic disease where EGFR mutations drive tumor growth.

• Non‑small cell lung cancer (NSCLC) with EGFR‑activating mutations: improves progression‑free survival in affected patients.
• Advanced EGFR‑mutated NSCLC: delays disease progression when used as first‑line therapy.
• Metastatic EGFR‑mutated NSCLC: provides a targeted oral option for patients with disseminated disease.

• Gefitinib reversibly binds to the intracellular ATP‑binding site of the epidermal growth factor receptor (EGFR) tyrosine kinase, inhibiting autophosphorylation and downstream signaling pathways such as MAPK, PI3K/AKT, and STAT. This blockade reduces cellular proliferation, survival, angiogenesis, and metastasis in tumor cells that depend on EGFR signaling.

Gefitinib may cause a range of adverse reactions, from mild to severe.

Common Side Effects

• Diarrhea: watery stools occurring in many patients.
• Rash: acne‑like skin eruptions, especially on the face and trunk.
• Nausea: mild to moderate upset stomach.
• Vomiting: occasional episodes of emesis.
• Decreased appetite: reduced food intake.
• Fatigue: generalized tiredness.

Serious or Rare Side Effects

• Interstitial lung disease: cough, dyspnea, and potentially fatal pulmonary inflammation.
• Hepatotoxicity: elevated liver enzymes and possible liver failure.
• Severe skin reactions: Stevens‑Johnson syndrome or toxic epidermal necrolysis.
• QT interval prolongation: risk of cardiac arrhythmias.
• Ocular disorders: blurred vision or retinal detachment.
• Severe hepatic failure: jaundice, coagulopathy, and hepatic encephalopathy.

Before initiating Gefitinib therapy, several safety considerations should be reviewed.

• Pregnancy: contraindicated (Category D) – avoid use during pregnancy.
• Liver function: monitor hepatic enzymes regularly; adjust therapy if significant elevation occurs.
• Skin reactions: inspect skin frequently for severe rash or desquamation.
• Pulmonary health: assess for new cough or dyspnea that may signal interstitial lung disease.
• Drug interactions: review concomitant CYP3A4 inhibitors or inducers.
• Store at ambient temperature: keep below 25 °C, retain in the original packaging, and protect from moisture.

Gefitinib can interact with several medicines, altering its efficacy or safety.

Major Interactions (Avoid)

• Strong CYP3A4 inhibitors (e.g., ketoconazole, clarithromycin): may increase gefitinib plasma levels.
• Antacids containing aluminum or magnesium: can reduce absorption if taken simultaneously.

Moderate Interactions (Monitor Closely)

• Moderate CYP3A4 inhibitors (e.g., fluconazole, erythromycin): may modestly raise drug exposure.
• Warfarin: potential increase in anticoagulant effect; monitor INR.
• Smoking: induces CYP1A1/1A2, potentially lowering gefitinib concentrations.
• Proton pump inhibitors: may affect gastric pH and drug absorption.
• Other EGFR inhibitors: concurrent use can increase toxicity risk.