The mechanism of the clinical antitumor action of Gefitinib is not fully characterized. Gefitinib inhibits the intracellular phosphorylation of numerous tyrosine kinases associated with transmembrane cell surface receptors, including the tyrosine kinases associated with the epidermal growth factor receptor (EGFR TK). EGFR is expressed on the cell surface of many normal cells and cancer cells.

Gefitinib is indicated for the first-line treatment of patients with metastatic non-small cell lung cancer (NSCLC) whose tumors have epidermal growth factor receptor (EGFR) exon 19 deletions or exon 21 (L858R) substitution mutations as detected by an FDA approved test.

The recommended dose of Gefitinib is 250 mg orally once daily with or without food until disease progression or unacceptable toxicity. Do not take a missed dose within 12 hours of the next dose. Administration to patients who have difficulty swallowing solid tablet, immerse Gefitinib tablets in 120/140ml of water by dropping the tablet in water, and stir for approximately 15 minutes. Immediately drink the liquid or administer through a naso-gastric tube.

1. Interstitial lung disease (ILD): ILD occurred in patients taking Gefitinib. Should withheld Gefitinib for worsening of respiratory symptoms. Need to discontinue Gefitinib if ILD is confirmed.

2. Hepatotoxicity: Should withheld Gefitinib for Grade 2 or higher for ALT and/or AST elevations. Should discontinue for severe hepatic impairment.

3. Gastrointestinal perforation: Discontinue Gefitinib for gastrointestinal perforation.

4. Diarrhea: Withhold Gefitinib for Grade 3 or higher diarrhea.

5. Ocular Disorders including Keratitis: For signs and symptoms of severe or worsening ocular disorders including keratitis Gefitinib should be withheld. 

6. Embryo-fetal Toxicity: Can cause fetal harm. Advise of potential risk to a fetus and use of effective contraception.

None

Pregnancy category D. If needed, patient should be imformed about the potential risk of Gefitinib.

Nursing mothers: Mother should be advised against breast feeding while receiving Gefitinib.

Pediatric Use: The safety and effectiveness of Gefitinib in pediatric patients have not been established.

Geriatric Use: No overall differences in safety or efficacy were observed between subjects 65 years and older and younger than 65. 

Gefikin 250 Tablet : Each box contains 4x7’s tablets in blister pack.

The most commonly reported adverse drug reactions (ADRs), reported in more than 20% of the patients and greater than placebo were skin reactions and diarrhea. There are some more adverse reactions such as:
 Interstitial Lung Disease
 Hepatotoxicity
 Gastrointestinal Perforation
 Severe or Persistent Diarrhea
 Ocular Disorders including Keratitis

Strong CYP3A4 Inducer: Concomitant administration of Rifampicin (600 mg QD for  16 days), a strong inducer of CYP3A4, with Gefitinib (500 mg single dose on Day 10 of  Gefitinib administration) reduced mean AUC of Gefitinib by 83%. CYP3A4 Inhibitor: Concomitant administration of Itraconazole (200 mg QD for 12 days), an inhibitor of CYP3A4, with Gefitinib (250 mg single dose on Day 4 of itraconazole administration) to healthy male subjects, increased mean Gefitinib AUC by 80%.

The acute toxicity of Gefitinib up to 500 mg in clinical studies has been low. Adverse reactions associated with overdose should be treated symptomatically; in particular, severe diarrhea should be managed appropriately.

Withhold for up to 14 days following adverse effects such as:
• Acute onset or worsening pulmonary symptoms (dyspnea, cough, fever)
• ≥ Grade 2 ALT and/or AST elevations
• ≥ Grade 3 diarrhea
• Signs and symptoms of severe or worsening ocular disorders including keratitis
• ≥ Grade 3 skin reactions

May resume Gefitinib when adverse effect fully resolves or improves to Grade 1.
Gefitinib should be discontinued for confirmed interstitial lung disease, severe hepatic
impairment, gastrointestinal perforation, persistent ulcerative keratitis.

Do not store above 30⁰ C. Protect from light. Keep out of reach of children.