Metoprolol is a potent and selective β1-adrenergic receptor blocker (Ki = 47 nM for the β1 receptor, compared with 3.0 and 10 μM for the β2 and β3 receptors, respectively). This product is a racemic mixture of enantiomers that differ in their in vivo actions and metabolism. Metoprolol is predominantly metabolized by the cytochrome P450 (CYP) isoform CYP2D6, an enzyme with significant genetic heterogeneity in function. The succinate salt of metoprolol is used in formulations intended for extended release of the compound. Beta-blockers, including metoprolol, have diverse applications in cardiology and vascular disease.
