It is a synthetic indirect-acting epinephrine-like drug that slowly and persistently constricts blood vessels and moderately increases myocardial contractility, thereby increasing cardiac blood output; it has a lighter effect on renal vasoconstriction, enhances blood flow to the brain, liver, kidney and coronary arteries, and has a long-lasting effect on blood pressure. It is metabolized by the liver, and the metabolites are excreted by the bile and kidney. The drug is commonly used for hypotension due to hemorrhage, drug allergy, surgical complications and traumatic brain injury or brain tumor combined with shock; to prevent and control acute hypotension occurring during intravertebral block anesthesia; also used for hypotension due to cardiogenic shock or sepsis. The use of this drug can cause acute pulmonary edema, cardiac arrhythmia, cardiac arrest when the response to elevation is too fast and too violent; overdose is manifested as convulsions, severe hypertension, severe arrhythmia, which should be immediately stopped for observation, and phentolamine can be given intravenously if the blood pressure is too high, and can be repeated if necessary; spillage of the drug during intravenous drip can cause severe local vasoconstriction, resulting in tissue necrosis and erosion or redness and hard nodules to form abscesses; long-term use Hypotension may occur when the drug is suddenly stopped.