Gefitinib is an oral, reversible, tyrosine kinase inhibitor of epidermal growth factor receptor (EGFR) that plays a key role in the biology of non-small cell lung cancer (NSCLC). First-line gefitinib for non-small cell lung cancer who were selected on the basis of epidermal growth factor receptor mutations improved PFS (Progression-Free Survival), with acceptable toxicity, in comparison to standard chemo. In order to treat non-small cell lung cancer, the standard dose of Gefitinib is 250 mg orally once a day either with or without food until the disease is progressive or in case of unacceptable toxicity. It is not advised to take a missed dose within 12 hours of the next dose.