(S)-Terazosin is an active S-enantiomer of Terazosin. (S)-Terazosin is a potent and high-affinity α-adrenoceptor antagonist with K i values of 3.91 nM, 0.79 nM and 1.16 nM for α1a , α1b and α1d-adrenoceptor , respectively. (S)-Terazosin also has high-affinity for α2a , α2B and α2c -adrenoceptor with K i values of 729 nM, 3.5 nM and 46.4 nM, respectively In Vitro The racemic compound and its enantiomers show high and apparently equal affinity for subtypes of α1-adrenoceptors with K i values in the low nanomolar range, and showed potent antagonism of α1-adrenoceptors in isolated tissues, with the enantiomers approximately equipotent to the racemate at each α1-adrenoceptor subtype. At α2b sites, (R)-Terazosin binds less potently than either the (S)-Terazosin or racemate. MCE has not independently confirmed the accuracy of these methods. They are for reference only. In Vivo (S)-Terazosin shows antagonism of at rat atrial α2B receptor with a pEC30 of 6.93. (s)-Terazosin shows antagonism of at rat vas deferens α1A and α2A receptor with pA2 values of 8.3 and 6.12, respectively . MCE has not independently confirmed the accuracy of these methods. They are for reference only. Form:Solid IC50& Target:Ki: 3.91 nM (α1a-adrenoceptor), 0.79 nM (α1b-adrenoceptor) and 1.16 nM (α1d-adrenoceptor),729 nM (α2a-adrenoceptor), 3.5 nM (α2Ba-adrenoceptor) and 46.4 nM (α2c-adrenoceptor)