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Inhibiting effect of droperidol compared with verapamil on the myocardial fiber calcium exchange determined by a simple physiological procedure.

A simple procedure was employed in order to quantify myocardial calcium antagonism by the neuroleptic agent droperidol. Droperidol blocked recovery of excitability induced by isoproterenol in isolated rabbit hearts depolarized by KCl. This was also observed with verapamil, a known calcium inhibitor, though at much lower concentrations. Considering that isoproterenol excites depolarized tissue by favouring calcium conductance and that droperidol as verapamil lack beta-adrenergic blocking properties, it is infered that droperidol hinders myocardial membrane permeability to calcium ions in a manner similar to that of verapamil. This action of droperidol, together with its known inhibiting effect on the rapid Na entrance, may explain the mechanism by which it affects cardiac chronotropism.