Terazosin hydrochloride acts as an α1- and α2B-adrenoceptor antagonist (Ki values are 3.3, 0.7, 1.1, 7.7, 1510 and 78.2 nM for α1A, α1B, α1D, α2B, α2A and α2C receptors respectively). Terazosin hydrochloride acts as an α1- and α2B-adrenoceptor antagonist (Ki values are 3.3, 0.7, 1.1, 7.7, 1510 and 78.2 nM for α1A, α1B, α1D, α2B, α2A and α2C receptors respectively). Terazosin hydrochloride has been used for orthogonality and similarity analysis using reversed-phase chromatographic studies. Furthermore, terazosin has also been used for the evaluation of chemometric techniques to determine orthogonality and similarity in chromatographic methods.