Phentolamine is a short-acting, non-selective alpha1 and alpha2 receptor blocker that decreases blood pressure by blocking alpha receptors and directly dilating blood vessels, resulting in a decrease in peripheral resistance. The main effects of phentolamine are rapid blood pressure lowering in patients with hypertensive crisis; for the treatment of intractable hypertension or aortic coarctation; also for diagnostic testing of pheochromocytoma; and also for the prevention of skin necrosis or decay following intravenous or extravenous norepinephrine administration. However, blood pressure and heart rate need to be monitored during administration. The elderly, children and patients with renal function problems should be considered carefully when using it, and it is best to apply intravenous pumping to facilitate dose control.