Gefitinib is not as effective as the side effects. Gefitinib is a drug that can be used to treat locally advanced or metastatic non-small cell lung cancer with sensitive mutations in the epidermal growth factor receptor gene; there is no inevitable connection between the efficacy of any drug and the non-size of its side effects, so there is no such thing as the greater the side effects of Gefitinib, the better the efficacy of Gefitinib. Adverse effects: Clinical studies have shown that the most common adverse effects caused by Gefitinib include diarrhea, rash, pruritus, dry skin, acne, anorexia, and weakness. CONTRAINDICATIONS: The drug is contraindicated in people with known hypersensitivity to any of the ingredients contained in Gefitinib. Precautions: Liver function should be checked regularly while using Gefitinib. If severe and persistent diarrhea, nausea, vomiting and other symptoms occur after use of the drug, seek immediate medical attention; consider discontinuing the drug if there are other adverse drug reactions, and promptly inform the physician for treatment. Gefitinib must be applied under the guidance of a specialized physician and should never be abused.