Efficacy and tolerance of tocainide during acute and long-term treatment of chronic ventricular arrhythmias

Summary

The acute efficacy of tocainide and procainamide was studied in 10 patients with chronic, reproducible ventricular arrhythmia. The drugs were administered in random order, by intravenous infusion, during repeated standardized, submaximal exercise tests. The proposed peak therapeutic plasma concentrations of both drugs were achieved. Both agents had an equal and statistically significant anti-arrhythmic effect; thus, a reduction in ventricular ectopic beat frequency by 70% or more was seen 9 patients after procainamide, and in 7 patients after tocainide. A fall in blood pressure was seen in two patients after procainamide and in one patient after tocainide. No other adverse reaction was observed. The long-term efficacy of tocainide was studied in 19 patients with chronic ventricular arrhythmias. All patients were monitored by 6–8-h electrocardiographic recordings, and 9 of them also during exercise tests. Tocainide 400 mg every 8 h resulted in a mean peak plasma tocainide concentration of 31.6 µmol/l, and caused suppression of ventricular extrasystolic beats by 70% or more in 11 patients. Adverse reactions to tocainide were seen in 14 patients. Gastro-intestinal and central nervous system side effects were most common, which often disappeared after a reduction in dose. In 5 patients adverse effects were more serious (one patient had syncope and 4 patients had skin rashes) and withdrawal of tocainide was required. Eight patients were treated with tocainide for more than 6 months, of whom 7 were restudied after withdrawal of tocainide; arrhythmias reappeared in 5.

The studies demonstrate that tocainide is an effective antiarrhythmic drug in selected patients, but the high frequency of adverse effects may limit its long-term use.