Beta-Blockers

1

What is the clinical pharmacology of β-adrenergic receptor blockers?

β-Adrenergic receptor blockers (beta-blockers) competitively inhibit the β-adrenergic receptors and by doing so act as antihypertensive drugs. Although the exact mechanisms through which these agents lower systemic blood pressure (BP) remain unclear, it is the blockade of the β ₁ -adrenergic receptor that appears to be the predominant mechanism by which these drugs reduce heart rate, cardiac output, and peripheral vascular resistance and thereby lower BP.

2

How are individual β-adrenergic receptor blockers different from each other?

Beta-blockers represent a heterogeneous class of antihypertensive compounds. As shown in Fig. 37.1 , these agents differ substantially in their β ₁ / β ₂ -adrenergic receptor selectivity, intrinsic sympathomimetic activity, and vasodilatory properties. Based on this diversity, beta-blockers have been classified into first-, second- and third-generation. First-generation includes non-cardioselective beta-blockers with equal affinity for β ₁ and β ₂ adrenergic receptors. Second-generation beta-blockers, also referred to as cardioselective beta-blockers, are characterized by greater affinity for β ₁ than for β ₂ adrenergic receptors. Neither of these two traditional categories exerts vasodilatory actions, which is an intrinsic property of third-generation beta-blockers.

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