Propranolol inhibits β1-, β2-, and β3-adrenergic receptors with log KD values of -8.16, -9.08, and -6.93, respectively. (±)-4-hydroxy Propranolol is an active metabolite of propranolol, inhibiting β1- and β2-adrenergic receptors with KD values of 2.4 and 5.8 nM, respectively. It is comparable to propranolol in potency in antagonizing the effects of isoprenaline on heart rate and blood pressure in cats and dogs. (±)-4-hydroxy Propranolol also has antioxidant properties at micromolar concentrations.
