Clinical efficacy and pharmacokinetics of a new orally effective antiarrhythmic, tocainide.

Tocainide, a new oral antiarrhythmic agent, was studied in man in a short-term protocol designed to evaluate the efficacy, kinetics, and toxicity of this compound. Premature ventricular contractions (PVCs) were suppressed by less than 70% in 11 of 15 patients compared with pre-drug placebo controls. For these 11 responders, there was an average PVC reduction of 91% +/- 10 (range 70 to 100%) at tocainide doses not associated with side effects. Mild transient central nervous system toxicity was observed in some patients near the time of peak concentrations during the highest dose administered. The drug was found to have linear kinetics over the dose range studied and a plasma half-life of 13.5 +/- 2 hours. Plasma concentration-response curves indicate antiarrhythmic activity over all plasma concentrations, with 70% PVC reduction above 6.0 mug/ml. This study suggests that tocainide is a safe and effective antiarrhythmic agent during short-term administration and is worthy of further clinical trials.