Home Drug Guide Gefitinib

Drug Guide

Generic Name

Gefitinib

Brand Names Iressa

Classification

Therapeutic: Antineoplastic (Lung Cancer)

Pharmacological: Epidermal Growth Factor Receptor (EGFR) Tyrosine Kinase Inhibitor

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

Assessment: Monitor for signs of lung toxicity, liver function tests, skin reactions, and diarrhea.

Diagnoses:

Risk for respiratory issues related to ILD
Risk for hepatotoxicity

Implementation: Regular monitoring of liver enzymes, pulmonary status, and skin assessments.

Evaluation: Evaluate for symptom resolution or progression, adverse effects, and lab abnormalities.

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.