Therapy Tocainide + Quinidine is More Effective than Monotherapy In patients with ventricular arrhythmias

11 men and 3 women of mean age 60 years, with> 30 ventricular premature complexes/hour on 48 hour ambulatory ECG, took part in a single-blind study. All patients had been previously treated unsuccessfully with other antiarrhythmic drugs including quinidine and procainamide. All patients received tocainide 400mg 8-hourly for 3 days following a placebo run-in. Tocainide dosage was then adjusted over the next 3 days, up to 1800mg daily or down to 600mg daily depending on response or adverse effects. Patients then received quinidine gluconate 324mg 8-hourly in addition to their titrated tocainide dose for 3 days, and then quinidine alone for 3 days.

Intolerable adverse effects prevented 3 patients from finishing the study. In the 10 patients completing the trial, tocainide alone was effective (~ 70% suppression of premature ventricular contractions and ~ 95% suppression of runs on 24 hour ambulatory ECG) in 2 patients, quinidine alone was effective in the same 2 patients and 1 other, and the combination was effective in these 3 patients plus 3 more. All 3 active treatments significantly reduced premature ventricular contractions, but tocainide alone and tocainide plus quinidine produced significantly greater suppression than quinidine alone. It was noted that plasma quinidine concentrations rose significantly after tocainide withdrawal. Tocainide shortened the OTe interval while quinidine prolonged it, and the combination treatment prolonged sinus-ectopic coupling.

The authors concluded that quinidine plus tocainide was more effective than either drug alone in suppressing ventricular arrhythmias, and the incidence of adverse effects with tocainide alone (7 patients) was reduced by dose reduction and efficacy was maintained when quinidine was added. Barbey JT. Thompson KA, Eeht OS. Woosley RL, Roden OM. American Journal of Cardiology 61 : 570·573, Mar 1988 .. "

6 INPHARMA'" 9 April 1988 0156-2703/88/0409·0006/ 0$01.00/ 0 © ADIS Press