Antiarrhythmic effects of tocainide and lidocaine in dogs

To compare the antiarrhythmic activities of tocainide and lidocaine in dogs, a protocol was designed where the drug plasma levels were increased stepwise. This was achieved by computerizing bolus doses and infusion rates, using pharmacokinetic equations with constants, derived from previous experiments in similar animals. In conscious coronary-ligated dogs with ischaemic arrhythmias both compounds were active, causing a 50% reduction in VPB's at plasma concentrations of 5.0 micrograms/ml (tocainide) and 3.5 micrograms/ml (lidocaine). "Clearing" of catecholamine-induced arrhythmias was not obtained in any of six dogs given tocainide and only in two out of six dogs given lidocaine.