Postsynaptic, selective a-adrenoreceptor antagonists lower blood pressure by decreasing peripheral vascular resistance. They are effective antihypeensive agents used either as monotherapy or in combination with other agents. However, in clinical trials of hypeensive patients, alpha blockade has not been shown to reduce cardiovascular morbidity and moality or to provide as much protection against CHF as other classes of antihypeensive agents. These agents are also effectivein treating lower urinary tract symptoms in men with prostatic hyperophy. Nonselective a-adrenoreceptor antagonists bind to postsynaptic and presynaptic receptors and are used primarily for the management of patients with pheochromocytoma. ref:harrison&;s principles of internal medicine,ed 18,pg no 4279