Gefitinib belongs to the class of drugs known as kinase inhibitors. It is used to treat non-small cell lung cancer that has progressed to other regions of the body in persons with specific types of malignancies. Gefitinib tablets are used in patients whose cancer has progressed to other regions of their bodies, who have faulty epidermal growth factor receptor genes, and who have not previously received cancer treatment. It acts by inhibiting the function of a naturally occurring chemical that may be required for cancer cell proliferation. The common side effects of Gefitinib tablets are diarrhea, nausea, vomiting, weakness, decreased appetite, fever, hair loss.