Phenobarbital, full name Phenobarbital Hydrochloride Tablets, usually needs to be taken for about two weeks before surgery. Phenobenzylamine hydrochloride tablets are a blocker of alpha 1 receptors and alpha 2 receptors, which after alpha receptor excitation leads to smooth muscle relaxation and vasodilation. Phenobenzylamine tablets are usually needed before surgery for pheochromocytoma, and have a dilating effect. It usually takes about two weeks before surgery with phenobenzylamine tablets. The use of phenobenzylamine hydrochloride tablets will cause the body’s peripheral blood vessels to dilate, and the body’s blood volume will increase, can be used to avoid after the removal of pheochromocytoma, the whole body’s blood vessels suddenly relax, a large dose of blood are accumulated in the body’s peripheral blood vessels, resulting in the emergence of low blood pressure shock. Phenobenzylamine Hydrochloride Tablets may cause a drop in blood pressure after use, requiring close monitoring of blood pressure changes. In addition, Phenobenzylamine Hydrochloride Tablets should be contraindicated for patients with angina pectoris and myocardial infarction, and if any adverse reaction occurs, it is necessary to give the correct treatment under the guidance of a doctor.