Biological Activity: | Subtype-selective α 1A -adrenoceptor antagonist that displays > 600-fold selectivity over other adrenoceptors (K i values are 0.35, 220, 370, 540, 800 and 1200 nM for α 1A , α 1B , α 2C , α 1D , α 2B and α 2A subtypes respectively and 540 nM for L-type Ca 2+ channels). Inhibits noradrenalin-induced contractions in rabbit vascular and lower urinary tissues. |