Abstract
The subdivision of β-receptors into β1-receptors (predominantly in the heart) and β2-receptors (lungs, blood vessels and elsewhere) was justified by the discovery that certain β-blockers such as practolol appeared to selectively block β1-receptors. It is now apparent that such cardioselectivity and the differential distribution of receptors are relative rather than absolute properties. The main applications for a β1-selective drug such as atenolol or metoprolol are considered to be in the treatment of patients with obstructive airways disease, diabetes mellitus or peripheral vascular disease. Theoretically, benefit could also be derived from the different effects of non-selective and selective drugs on peripheral blood vessels — the former block β2-mediated vasodilatation and should accentuate α-mediated vasoconstriction; the latter do not. Despite this, it has not been possible to show important differences in efficacy between the 2 groups of drugs in the long term managment of hypertension. However, more recently, interest has focused on the cardiovascular consequences of stresses such as cigarette smoking and it may be that cardioselective drugs will prove more protective for patients with hypertension and ischaemic heart disease. The final question for debate may be not whether cardioselective drugs offer advantages over non-selective drugs but whether there are any benefits in using non-selective β-adrenoceptor antagonists.
Published Version
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