Pharmacological profile of beta-adrenoceptor blockers with vasodilating properties, especially carvedilol--rationale for clinical use

Abstract

The rationale for the combined use of beta-adrenoceptor antagonists and vasodilators is to improve the efficacy of the antihypertensive therapy and to reduce the incidence of side effects. If suitable coagents are selected and used at appropriate doses, the disadvantages of each separate component (compromised blood flow to individual organs, increase in total peripheral resistance, unfavorable lipid profile for beta-blockers; stimulation of counter-regulatory mechanisms, retention of water and electrolytes for vasodilators) can be balanced. In addition, the favorable effects of each (reduction in cardiovascular morbidity and mortality for beta-blockers, and favorable hemodynamic profile for vasodilators) may be used to advantage. Such a treatment rationale can be accomplished by a free combination or by using a dual-acting drug. From the practical point of view, the latter may be preferable. The basic requirement for such a drug is that the two effects are evoked in the same dose range. Carvedilol is a dual-acting drug designed to produce beta-blockade and vasodilation in the same dose range. The vasodilation is mediated predominantly by specific alpha 1-adrenoceptor blockade; at markedly higher concentrations additional vasodilating actions can be observed. These effects resemble those of Ca(2+)-antagonistic properties. However, they do not contribute to the acute blood-pressure-lowering activity, but may be responsible for the increased blood flow to some organs. At beta-blocking doses, carvedilol reduces the total peripheral resistance, and blood flow to the kidneys is preserved. Cardioprotection has been demonstrated in a variety of experimental investigations.