Dosage of Gefitinib

Patient Selection

Select patients for first-line treatment of metastatic NSCLC with gefitinib based on the presence of EGFR exon 19 deletions or exon 21 L858R mutations in the patient’s tumor or plasma samples. If these mutations are not detected in plasma samples, tumor tissue should be tested if feasible.

Recommended Dosage

The recommended dose of gefitinib is 250 mg, administered orally once daily, with or without food, until disease progression or unacceptable toxicity occurs.

Do not make up for a missed dose within 12 hours before the next scheduled dose.

Administration in Patients with Difficulty Swallowing Solids

Place the gefitinib tablet in 4 to 8 ounces of water and stir for approximately 15 minutes after immersion. Drink the liquid immediately or administer via a nasogastric tube. Rinse the container with 4 to 8 ounces of water and drink or administer via nasogastric tube immediately.

Dosage Adjustment

Dosage Adjustment for Adverse ReactionsSuspend gefitinib (for up to 14 days) for any of the following conditions:

Acute onset or worsening of pulmonary symptoms (dyspnea, cough, fever).

Elevations in ALT and/or AST of NCI CTCAE Grade 2 or higher.

Diarrhea of NCI CTCAE Grade 3 or higher.

Signs and symptoms of severe or worsening ocular disorders (including keratitis).

Skin reactions of NCI CTCAE Grade 3 or higher.

Resume gefitinib treatment when adverse reactions have fully resolved or improved to NCI CTCAE Grade 1.

Permanently discontinue gefitinib for:

Confirmed interstitial lung disease (ILD).

Severe hepatic impairment.

Gastrointestinal perforation.

Persistent ulcerative keratitis.

Dosage Adjustment for Drug Interactions

Strong CYP3A4 Inducers

In the absence of severe adverse reactions, increase the gefitinib dose to 500 mg once daily, and resume the 250 mg dose of gefitinib seven days after discontinuing the strong CYP3A4 inducer.

FDA，2021.05