Phentolamine mesylate is primarily used in medical settings to manage high blood pressure episodes caused by certain conditions, such as pheochromocytoma, a rare tumor of the adrenal gland. It works by blocking alpha-adrenergic receptors, leading to the relaxation of blood vessels and improved blood flow. This medication is also employed to reverse the effects of local anesthetics containing vasoconstrictors, such as epinephrine, particularly in dental procedures to prevent prolonged numbness or tissue damage. Additionally, it is used in diagnostic tests for autonomic nervous system disorders to assess vascular responsiveness. In some cases, it is applied topically or via injection to treat conditions like erectile dysfunction or priapism by promoting or regulating blood flow to the affected area. Its versatility in addressing vascular and hypertensive issues makes it a valuable tool in both therapeutic and diagnostic contexts.