Zinterol hydrochloride (MJ 9184 hydrochloride) is a potent and selective β2-adrenoceptor agonist^[1]. Zinterol increases I_Ca in a concentration-dependent manner with an EC₅₀ of 2.2 nM^[2]. IC50 & Target: β2-adrenoceptor^[1] In Vivo: Zinterol (2.5 μg/kg i.v. bolus over 5 s) leads to ventricular arrhythmias including premature ventricular complexes (PVCs) and runs of ventricular tachycardia (VT) in heart failure (HF) rabbits. Zinterol at a lower dose (1 μg/kg i.v, n=4) does not induce ventricular arrhythmias in HF rabbits^[3].