Mexiletine and quinidine in ventricular ectopy

The antidysrhythmic efficacy and tolerance of mexiletine and quinidine were compared in 26 ambulatory patients with chronic ventricular ectopy. Thirteen patients were treated with mexiletine and 13 with quinidine. The treatment groups were comparable in age and cardiac diagnoses, in frequency of untreated ventricular ectopy, in the presence of complex forms, and in previous drug failures. After two 24-hr ambulatory ECG recordings, the patients were treated according to a double-blind, dose-ranging protocol. Efficacy was defined as reduction in ventricular ectopic frequency by at least 70% in a comparison of two 24-hr ambulatory ECG recordings after drug with the two pretreatment recordings. Suppression of ventricular ectopic frequency by at least 70% was achieved in seven mexiletine-treated patients and eight quinidine-treated patients. Neither drug consistently abolished complex forms of ectopy. The incidence of adverse effects was of the same order in the two groups. We conclude that mexiletine is as effective as quinidine in the suppression of ventricular ectopy. Use of both drugs is limited by adverse effects.