On the kinetics and dynamics of tocainide and its metabolites

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Abstract
The kinetics of tocainide, a new antiarrhythmic, and 2 of its metabolites, lactoxylidide (LX) and tocainide carbamoyl glucuronide (TG), were examined in patients given tocainide for 7 days following an acute myocardial infarction. In these patients kinetics were much the same as those reported for volunteers and for patients treated with tocainide for chronic extra ventricular beats. Mean half-lifes for tocainide, LX and TG were 13.6, 29.1 and 13 h. At steady state, mean metabolite to tocainide ratios in serum were 0.48 for LX and 0.28 for TG. Using animal models [mouse, rabbit] the relative antiarrhythmic, direct cardiac and CNS effects of tocainide and LX were examined. LX, the deaminated alcohol metabolite, had no antiarrhythmic, direct cardiac or CNS toxic effects. Evidently, tocainide, unlike many antiarrhythmic drugs, has no active metabolites.