(R)-Propranolol hydrochloride (Dexpropranolol hydrochloride) is the less active enantiomer of the anti-adrenoceptor (β-adrenoceptor) antagonist propranolol. Propranolol is a nonselective β-adrenergic receptor (βAR) antagonist with a high affinity for β1AR and β2AR with Ki values of 1.8 nM and 0.8 nM, respectively.

β2-adrenoceptor:0.8 nM(Ki), β1-adrenoceptor:1.8 nM(Ki)

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].