Propranolol:



Chiral carbon: Propranolol has two chiral carbons, one at the C-1 position and the other at the C-2 position. The C-1 position has an S configuration, while the C-2 position has an R configuration.

Atenolol:



Chiral carbon: Atenolol has one chiral carbon at the C-2 position, which has an S configuration.



Propranolol is metabolized in the liver by the cytochrome P450 enzyme system. The metabolism of propranolol involves two major pathways:

1. Oxidative metabolism: In this pathway, propranolol is first converted to its active metabolite, 4-hydroxypropranolol, by the cytochrome P450 2D6 (CYP2D6) enzyme. This metabolite is further oxidized to form other metabolites, such as naphthoxylactic acid, which are excreted in the urine.

2. Conjugative metabolism: In this pathway, propranolol is metabolized into glucuronide and sulfate conjugates, which are excreted in the urine. This pathway is mediated by the uridine diphosphate glucuronosyltransferase (UGT) and sulfotransferase (SULT) enzymes.

The metabolism of propranolol can be affected by several factors, such as genetic polymorphisms in the CYP2D6 enzyme, drug interactions, liver disease, and age. In individuals who are poor metabolizers of propranolol, the drug may accumulate in the body, leading to increased risk of adverse effects.