RX821002 is a potent and selective antagonist of α2-adrenoceptor with low affinity for imidazoline sites. RX821002 displays selectivity for the α2D over the α2A subtypes (pKd values are 9.7 and 8.2 respectively).
Fenoldopam hydrochloride is a selective D1-like dopamine receptor partial agonist. It acts as a vasodilator in vivo and does not readily cross the blood-brain barrier. Fenoldopam HCl is also an α2-adrenoceptor antagonist in vitro.