The loading dose of dexmedetomidine used in painless gastroscopy is generally 1 μg/kg continuously pumped over 10 to 15 minutes. The loading dose for continuous pumping in painless gastroscopy is 1 μg/kg for 10-15 minutes, and the later maintenance dose is 0.2-0.7 μg/(kg-h), which can reduce the pain of patients and keep them quiet during gastroscopy. However, the specific dosage should also consider the patient’s sensitivity to the drug and so on. Adverse effects of dexmedetomidine include hypotension, bradycardia, temporary hypertension, and liver damage. Dexmedetomidine is contraindicated in people who are allergic to dexmedetomidine and its components. The dosage should be chosen carefully for patients with renal insufficiency, liver damage, etc., as well as for pregnant women and children. The drug should be used only under the guidance of a specialized physician, and should not be used blindly on its own to avoid adverse reactions.