A subtype-selective ligand for the α1B-adrenoceptor. The pKi values for binding to rat fibroblast cell membranes expressing α1B (hamster), α1A (bovine) and α1D (rat) are 7.1, 5.59, and 5.68 respectively. Appears to be non-selective between α1 subtypes and α2 receptors in smooth muscle preparations.