Efficacy of oral mexiletine therapy at a 12-h dosage interval.

The antiarrhythmic effectiveness and safety of 12-h oral administration of mexiletine were evaluated in adult outpatients with a baseline hourly rate of PVCs of 30 or higher who had initially shown at least a 50 percent reduction of this rate when treated with mexiletine at an 8-h dosage interval. Doses were titrated on the basis of 24-h Holter monitoring for both 8- and 12-h intervals. Seventeen of 26 patients showed PVC reductions after 8-h treatment. Fifteen of these 17 patients reached the goal reduction of greater than or equal to 50 percent in the hourly PCV rate with 12-h dosing. Hour-by-hour analysis disclosed a consistent degree of PVC suppression throughout both 8- and 12-h dose intervals. No increase in the incidence of adverse effects was associated with conversion to the 12-h regimen.