What are beta blockers?

        Drugs which inhibit adrenergic responses mediated through beta receptors. They are all Competitive antagonists.

General Structure of Beta Block

SAR of Beta Blockers

The aromatic ring and its substituent is the primary determinant of β1 antagonistic activity. It also affects the absorption, excretion, and metabolism of the β blockers.

β blockers are structurally similar to β agonist. The catechol ring can be replaced by a variety of ring system without loss of antagonistic activity.

The two carbon chains are essential for activity. 

The introduction of -OCH2 group into the molecule between the aromatic ring and the ethyl amine side chain provides β blocking agents, for example, propranolol.

Must be a secondary amine for optimal activity. 

As with the sympathomimetic agents, the configuration of the hydroxyl bearing carbon of the aryloxypropanolamine side chain play a critical role in the interaction  of β antagonist drugs with β receptor. The carbon must possess the (S) configuration for optimal affinity to the β receptor. The enantiomer with the (R) configuration is typically 100 times less potent.