Phenoxybenzamine is a noncompetitive, irreversible α-adrenergic receptor antagonist (IC50 = 34.2 nM for α1; Kis = 0.06, 0.01, and 0.06 μM for α2A, α2B, and α2C, respectively) with antihypertensive activity. It forms a covalent bond with the adrenergic receptor, resulting in a slow onset and highly prolonged duration (2-8 days) of the blockade that subsides upon the synthesis of new adrenergic receptors. Due to its ability to selectively block longitudinal but not circular muscle contraction in human vas deferens, phenoxybenzamine has been explored as a form of male contraception to prevent sperm emission. The ability of phenoxybenzamine to block sympathetic signal transduction has also been explored in the context of complex regional pain syndrome.
