Notes: Norpropranolol is an active metabolite of the β-adrenergic receptor (β-AR) antagonist propranolol (Item No. 23349).{54827,33933} It is formed from propranolol by the cytochrome P450 (CYP) isoform CYP1A2.{33933} Norpropranolol binds to β-ARs (Kd = 42 nM in turkey erythrocytes) and inhibits (–)-isoproterenol-induced activation of adenylate cyclase with a Ki value of 175 nM.{54827}