Phentolamine is a short-acting, non-selective α1 and α2 receptor blocker that decreases blood pressure by blocking α receptors and directly dilating blood vessels, resulting in a decrease in peripheral resistance. The indications for Phentolamine are rapid blood pressure lowering in patients with hypertensive crisis, antihypertensive treatment for refractory hypertension or aortic coarctation, diagnostic testing for pheochromocytoma, and skin necrosis or decomposition following intravenous or parenteral administration of norepinephrine. Phentolamine is usually a prescription medication and should be purchased as directed by a doctor and with a doctor’s prescription. It is important not to increase the dosage of this medication, as overdose may cause serious adverse effects such as tachycardia or arrhythmia. The main adverse reactions are low arterial blood pressure, reflex tachycardia, arrhythmia, increased systemic venous volume and possible shock, which may be accompanied by headache, hyperventilation, visual disturbances, sweating, vomiting, diarrhea and hypoglycemia. Contraindications are: hypersensitivity to phentolamine and related compounds, hypersensitivity to sulfites; hypotension, severe atherosclerosis, angina pectoris, myocardial infarction, gastric and duodenal ulcers; renal insufficiency; children, senior citizens. Blood pressure and heart rate need to be monitored during the use of the drug. Elderly people, children and patients with renal function problems should consider the use of this drug carefully and use it under the supervision of a physician.