Gefitinib is a kind of targeted drug, in the treatment of non-small cell lung cancer, it can kill the cancer cells directly and will not damage the normal cells. Interstitial pneumonitis occurs in some patients while taking the drug, and the drug should be stopped promptly. Gefitinib is a tyrosine kinase inhibitor, which is the first generation of targeted drugs for the treatment of non-small cell lung cancer, and it can also be used for patients who have previously failed to use chemotherapy. Gefitinib can inhibit epidermal growth factor by inhibiting tyrosine kinase, so as to achieve the purpose of anti-tumor, Gefitinib can inhibit tumor growth and metastasis, so as to promote the apoptosis of tumor cells. Patients must undergo genetic testing before using this drug, and only those who are sensitive to this drug can benefit from genetic testing. During the use of this drug, attention should be paid to monitoring patients for adverse reactions such as rash, diarrhea, and bone marrow suppression, which are usually reversible and will get better after discontinuing the drug, and do not require special treatment. Some patients may suffer from interstitial pneumonitis while taking the drug, once this happens, the drug should be stopped promptly. The drug should be used with caution in patients with pulmonary fibrosis and impaired lung function; it is contraindicated in those who are allergic to the product and its components. The drug needs to be used under the guidance of a doctor, do not blindly use the drug on your own to avoid adverse consequences.