The effects of alifedrine, a positive inotropic agent, were examined in greyhounds anaesthetised with chloralose. An intravenous dose of 0.3 mg kg-1 resulted in a substantial increase in myocardial contractility (increased dP/dtmax, cardiac output and stroke volume) without significantly affecting heart rate. The effects of alifedrine on the severity of arrhythmias resulting from both coronary artery occlusion and reperfusion were also determined. A mild anti-arrhythmic effect was observed during early ischaemia when the incidence of ventricular tachycardia was reduced from 90% in controls to 50% in treated dogs. There was also a significant reduction in the number of extrasystoles appearing as ventricular tachycardia (from 511 ± 138 to 151 ± 84). The total number of extrasystoles during the first 30 min of ischaemia was also reduced, although not significantly, from 846 ± 193 to 527 ± 86. Following release of a 40 min coronary artery occlusion there was a marked reduction in reperfusion-induced ventricular fibrillation from 75% in controls, to 37% in the alifedrine-treated dogs. The overall survival from the combined occlusion-reperfusion insult was increased from 20% in controls to 50%. These results suggest that alifedrine has an unusual and useful spectrum of pharmacological activity in that it combines antiarrhythmic activity with an ability to improve cardiac function.
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