Mexiletine: double-blind comparison with procainamide in PVC suppression and open-label sequential comparison with amiodarone in life-threatening ventricular arrhythmias.

The antiarrhythmic effects of mexiletine (n = 14) were compared to procainamide (n = 16) by a double-blind parallel protocol in 30 patients (group I) with frequent premature ventricular contractions (PVCs) (greater than 20/hr), and to amiodarone by an open-label sequential approach in 25 patients (mean left ventricular ejection fraction of 32.6 +/- 13.4%) with life-threatening ventricular arrhythmias (group II) resistant to two or more conventional agents. The predetermined end point of therapy in group I patients was met in 6 of 14 (43%) given mexiletine, with 7 (50%) requiring drug discontinuation for severe gastrointestinal or central nervous system side effects and only 3 of 16 patients (19%) given procainamide, with 5 (31%) developing limiting side effects. Increases in dose led to a higher efficacy rate for PVC suppression with a corresponding increase in side effects with mexiletine; with procainamide, the higher dose was not associated with greater PVC suppression. In group II patients, mexiletine was effective in 4 (16%), with one patient discontinuing the drug during long-term therapy; mexiletine was ineffective in 16 (64%) and early side effects developed in 5 (20%). Patients not responding to or not tolerating mexiletine were given amiodarone; 20 of 21 (95%) responded with arrhythmia control after the loading dose. During a mean follow-up period of 2 years, sudden death occurred in two patients, death from heart failure in two, and death from subarachnoid hemorrhage in one patient; 15 (75%) patients are alive and free of arrhythmia.(ABSTRACT TRUNCATED AT 250 WORDS)