Both isomers of propranolol are capable of preventing adrenaline-induced cardiac arrhythmias in cats anaesthetized with halothane and reversing ventricular tachycardia caused by ouabain in anaesthetized cats and dogs, but the dose of (-)-propranolol is significantly smaller than that of (+)-propranolol ((R)-Propranolol) in both species[4]. Administration of 10 mg/kg (R)-Propranolol hydrochloride has no antagonistic activity in rats, the cardiac responses to isoprenaline of rats can be blocked by probably much less than 1/100th of that of the (-) isomer in this preparation[4].