Comparative haemodynamic effects of lidocaine, mexiletine, and disopyramide. 
The effect of intravenous boluses of lidocaine (5 mg/kg), mexiletine (3.5 mg/kg), and disopyramide (5 mg/kg) on mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), total peripheral resistance, left ventricular end-diastolic pressure, and peak rate of change of left ventricular pressure (peak LV dP/dt) were assessed in the conscious rabbit.  Plasma levels for the three drugs corresponded to the human therapeutic range 3 min after administration.  All three drugs had negative inotropic effects and reduced HR.  Lidocaine reduced peak LV dP/dt by 26%, mexiletine by 41%, and disopyramide by 53%.  The three drugs had quite different effects on CO as a result of differences in their actions on peripheral blood vessels: disopyramide caused a 21% fall in CO, associated with a significant vasoconstriction; mexiletine did not lower CO, as it caused a substantial vasodilation; and lidocaine did not produce any substantial change in either CO or vascular resistance.  Cardiac autonomic blockade did not alter these changes.  These results confirm that disopyramide has a marked cardiodepressant effect, and demonstrate that, although lidocaine depresses myocardial contractility in the conscious rabbit, it has little effect on other haemodynamic parameters.  The experiments also show that mexiletine is a more profound negative inotrope than lidocaine, but that, as it produces a significant fall in MAP and thus a reduction in afterload, the CO is maintained.