Generic Name

Gefitinib

---

Classification

FDA Approved Indications

• Treatment of locally advanced or metastatic non-small cell lung cancer (NSCLC) with EGFR exon 19 deletions or exon 21 L858R substitutions after failure of platinum-based chemotherapy

Mechanism of Action

Gefitinib inhibits the tyrosine kinase activity of the EGFR, blocking downstream signaling pathways that promote cell proliferation and survival in EGFR-mutated cancer cells.

Dosage and Administration

Adult: 250 mg once daily, with or without food.

Pediatric: Not approved for pediatric use.

Geriatric: Use with caution, no specific dose adjustment if renal and hepatic functions are normal.

Renal Impairment: Use caution; no specific dose adjustment recommended.

Hepatic Impairment: Start at lower dose; monitor closely.

Pharmacokinetics

Absorption: Well absorbed orally, peak plasma levels in 4 hours.

Distribution: Approximately 93% bound to plasma proteins.

Metabolism: Primarily by hepatic CYP3A4, also CYP2D6, CYP1A1, CYP2C8.

Excretion: Feces (83%), urine (9%).

Half Life: 41 hours.

Contraindications

• Hypersensitivity to gefitinib or excipients.

Precautions

• Lung toxicity, interstitial pneumonia, hepatotoxicity, skin reactions, diarrhea, ocular effects, use with caution in patients with pre-existing lung disease or hepatic impairment.

Adverse Reactions - Common

• Diarrhea (Very common)
• Rash (Common)
• Nausea (Common)

Adverse Reactions - Serious

• Interstitial Lung Disease (ILD) (Rare but serious)
• Hepatotoxicity leading to hepatitis or liver failure (Rare)

Drug-Drug Interactions

• CYP3A4 inhibitors (e.g., ketoconazole), CYP3A4 inducers (e.g., rifampin), warfarin.

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Patient/Family Teaching

• Report any new or worsening cough, difficulty breathing, or chest pain.
• Avoid sun exposure, use sunscreen to prevent rash.
• Report signs of liver toxicity such as jaundice, dark urine.

Special Considerations

Black Box Warnings:

• Interstitial Lung Disease, that can be fatal.
• Emphasize importance of early reporting of pulmonary symptoms.

Genetic Factors: Efficacy depends on tumor EGFR mutation status.

Lab Test Interference: None known.

Overdose Management

Signs/Symptoms: Severe diarrhea, rash, hepatotoxicity.

Treatment: Supportive care, symptomatic treatment, and consult poison control.

Storage and Handling

Storage: Store at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F to 86°F).

Stability: Stable for up to 2 years when stored properly.