(R)-Terazosin is an active R-enantiomer of Terazosin. (R)-Terazosin is a potent α1-adrenoceptor antagonist with K i values of 6.51 nM, 1.01 nM and 1.97 nM for α1a , α1b and α1d-adrenoceptor , respectively In Vitro (R)-Terazosin is low affinity for α2a, α2B and α2c-adrenoceptor with K i values of 3.85 μM, 0.33 μM and 0.37 μM, respectively. (R)-Terazosin may prove to be a useful probe in understanding the functional role of subtypes of adrenoceptors in various tissues. Because it is a weaker antagonist at α2B sites than its enantiomer, it may be possible to use (R)-Terazosin to differentiate between pharmacological effects mediated by subtypes of α2-adrenoceptors in animal studies. MCE has not independently confirmed the accuracy of these methods. They are for reference only. In Vivo (R)-Terazosin shows antagonism of at rat atrial α2B receptor with a pEC 30 of 5.69. (R)-Terazosin shows antagonism of at rat vas deferens α1A and α2A receptor with pA 2 values of 7.5 and 5.31, respectively . MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:Ki: 6.51 nM (α1a-adrenoceptor), 1.01 nM (α1b-adrenoceptor) and 1.97 nM (α1d-adrenoceptor)