ERSA, also known as Gefitinib, is a powerful EGFR tyrosine kinase inhibitor that acts as a blocker of the signal transduction pathway for proliferation, growth, and survival of cancer cells. Currently, Gefitinib is available in boxes of 10 tablets, each tablet is 250mg, and the price per box is around 2300 RMB. It is mainly used for the treatment of non-small cell lung cancer and is more effective in patients with adenocarcinoma, women, and non-smokers. It is taken orally, 250mg each time, once a day, on an empty stomach or at the same time as food. No dose adjustment is usually required based on the patient’s age, weight, gender, and renal insufficiency. The most common adverse reactions are diarrhea, rash, pruritus, dry skin and acne, occurring in more than 20% of cases, seen within 1 month of taking the drug, and are usually reversible.