The actions of felodipine on arrhythmias and other responses to myocardial ischaemia in conscious rats.

The antiarrhythmic activity of felodipine was investigated in conscious chronically prepared rats subjected to coronary artery occlusion. By deliberate high or low placement of an occluder, either large or small occluded zones were produced. In rats with small occluded zones (SOZ), felodipine i.v. (0.2 mumol/kg slow injection + 0.01 mumol/kg per min infusion, and 12.2 mumol/kg slow injection) possessed slight antiarrhythmic activity. In rats with large occluded zones (LOZ), similar doses of felodipine had little antiarrhythmic activity. Felodipine produced a dose-dependent reduction in blood-pressure and delayed the development of ECG signs of ischaemia (ST elevation). The occluded zone size was not reduced by felodipine, although some myocardial salvage (8-17%) may have occurred in SOZ rats. It is concluded that felodipine, at doses producing severe hypotension associated with vasodilatation, possesses little antiarrhythmic activity.