Used primarily to treat high blood pressure caused by pheochromocytoma, a tumor of the adrenal gland. It helps block the effects of certain hormones like norepinephrine, which can constrict blood vessels and raise blood pressure. Also used to manage symptoms of cocaine intoxication involving severe hypertension. In some cases, it is administered to reverse the effects of vasoconstrictors used in dental procedures, helping to prolong anesthesia and reduce tissue damage. Additionally, it has been used off-label to treat erectile dysfunction by improving blood flow when injected directly into the penis. Its ability to dilate blood vessels makes it useful in diagnostic tests for Raynaud's phenomenon and other circulatory conditions.