A high-affinity, lipophilic, non-selective ligand of the β-adrenergic receptors (Kis = 0.114 and 0.4 nM for β2- and β3-adrenoceptors, respectively); acts as a receptor antagonist (beta blocker) or inverse agonist for β1 and β2 receptors but functions as an agonist at the β3-adrenergic receptor