Mexiletine therapy in 15 patients with drug-resistant ventricular tachycardia.

Mexiletine therapy was administered to 15 patients with chronic and recurrent episodes of ventricular tachycardia or ventricular fibrillation. All patients were intolerant of or had arrhythmias resistant to conventional antiarrhythmic agents. At maximal dosages of mexiletine 2 patients had more than 90 percent reduction in frequency of premature ventricular complexes, whereas 11 patients had less than 50 percent reduction, as measured on 24 hour electrocardiographic recordings. Mexiletine was unsuccessful in preventing or abolishing ventricular tachycardia in 11 patients. Adverse side effects occurred in nine patients (60 percent) and were severe enough to necessitate discontinuation of therapy in six patients (40 percent). Side effects appeared to be dosage-related. Pharmacokinetic analysis indicated a mean elimination half-life of 12.6 +/- 1.6 hours following oral administration of mexiletine. In the patients studied, mexiletine exhibited limited antiarrhythmic efficacy and was associated with frequent adverse side effects.