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The mechanism of action of calcium antagonists relative to their clinical applications.
Author(s) -
Singh BN
Publication year - 1986
Publication title -
british journal of clinical pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.216
H-Index - 146
eISSN - 1365-2125
pISSN - 0306-5251
DOI - 10.1111/j.1365-2125.1986.tb02860.x
Subject(s) - bepridil , medicine , flunarizine , verapamil , gallopamil , nifedipine , cinnarizine , pharmacology , diltiazem , vasodilation , peripheral , calcium , cardiology
As a class of therapeutic agents calcium antagonists have attracted increasing attention in recent years. Their major indications have been in the treatment of ischaemic myocardial syndromes, certain cardiac arrhythmias, hypertension, obstructive cardiomyopathies, and a number of lesser clinical disorders in which their role is less clearly defined. With the widening spectrum of therapeutic utility and an increasing plethora of newer agents under development, it is of importance to relate the overall pharmacodynamics of individual agents to their clinical effects. Calcium antagonists have a variable specificity for cardiac and peripheral activity. Based on such activity, it is useful to construct a classification of these compounds, new and old, into four categories. Type I agents, typified by verapamil and its congeners (tiapamil and gallopamil) and diltiazem, prolong AV nodal conduction and refractoriness with little effect on ventricular or atrial refractory period. These actions account for their direct antiarrhythmic properties. Type II agents include nifedipine and other dihydropyridines. In vivo, these agents are devoid of electrophysiologic effects in usual doses. They are potent peripheral vasodilators with some selectivity of action for different vascular beds; their overall haemodynamic effects are dominated by this peripheral vasodilatation and reflex augmentation of sympathetic reflexes. Type III agents include flunarizine and cinnarizine (piperazine derivatives), which, in vitro and in vivo, are potent dilators of peripheral vessels, with no corresponding calcium‐blocking actions in the heart. Type IV agents are agents with a broader pharmacologic profile (perhexiline, lidoflazine and bepridil); they block calcium fluxes in the heart, in the peripheral vessels, or both. They may inhibit the fast channel in the heart and have other electrophysiologic actions. A clear understanding of the varied pharmacologic properties of the different classes of calcium antagonists is likely to provide a rational basis for the use of these agents in clinical therapeutics.