Phentolamine hydrochloride

Phentolamine hydrochloride is a potent, selective, and orally active antagonist of α1 and α2 adrenergic receptors , with pKi values of 8.8, 8.0, and 8.3 for the human α2A, α2B, and α2C adrenergic receptors, respectively. It also shows binding affinities for the α1-adrenoceptor subtypes, exhibiting Ki values of 6.1 nM for cloned α1A/D, 39.8 nM for α1B, and 2.8 nM for α1C.