[A synthetic, dibenzamine alpha-adrenergic antagonist with antihypertensive and vasodilatory properties. Phenoxybenzamine non-selectively and irreversibly blocks the postsynaptic alpha-adrenergic receptor in smooth muscle, thereby preventing vasoconstriction, relieving vasospasms, and decreasing peripheral resistance. Reflex tachycardia may occur and may be enhanced by blockade of alpha2 receptors which enhances norepinephrine release. Phenoxybenzamine is reasonably anticipated to be a human carcinogen. ( NCI )] (UMLS (NCI) C0031441) =Organic Chemical; Pharmacologic Substance ; =Ethylamines; sympatholytic agent =PHENOXYBENZAMINE HYDROCHLORIDE