Beta-blocking agents with vasodilator activity


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Abstract

Use of non-selective β-blockers: Non-selective β-blockers reduce blood pressure by reducing cardiac output. They have a proven record of efficacy, alone or in combination with other drug classes, in the treatment of hypertension, ischemic heart disease and some tachyarrhythmias. They have also proved effective in the primary and secondary prevention of myocardial infarction. However, adverse effects include increased peripheral resistance, limitation of exercise tolerance, and bradyarrhythmia, cold extremities and bronchoconstriction in susceptible patients.Effects of β1-selective blockers: β1-Selective antagonists cause less vasoconstriction and less bronchoconstriction than non-selective β-blockers, but the reduction in cardiac output may still activate a sympathetically mediated increase in peripheral resistance. β1-blockers with β2 agonist activity are vasodilatory because they activate postsynaptic β2 receptors on vascular smooth muscle cell membranes, via the formation of cyclic AMP.Non-selective β-blockers with α2-adrenoceptor blocking activity: Non-selective β-adrenoceptor blockers with α1-adrenoceptor blocking activity, such as carvedilol, labetalol, medroxalol and bucindolol, combine the advantages of β- and α1-blockade, including peripheral vasodilation. As an example of this class of agent, carvedilol has been shown to be effective in the treatment of hypertension by reducing peripheral resistance. There are some indications, still to be confirmed, that it improves left ventricular diastolic function and causes regression of left ventricular hypertrophy, and that it may be useful in the treatment of some patients with congestive heart failure or arrythmia. In animal models of myocardial ischemia, carvedilol has proved to be cardioprotective.

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