Slow-release mexiletine in the treatment of ventricular premature beats. Comparison with long-acting dihydroquinidine

This double-blind, placebo-controlled, cross-over study was designed to compare the efficacy of orally administered slow-release mexiletine (SM) (360 mg 2 bid for 5 days) and long-acting dihydroquinidine (LD) (250 mg 2 bid for 5 days) in reducing ventricular premature beats (VPBs). The protocol was completed by 12 hospitalized patients. Entry was determined by the presence of more than 720 VPBs in 2 pre-trial 24 hours Holter monitorings. The study protocol was as follows: during the 1st, 3rd and 5th three-day periods, each patient received the placebo of both drugs on single blind condition; during the 2nd and 4th five-day periods, the patients were given on double blind condition SM or LD (double dummy technique) and placebo of the other drug according to a cross-over design. The 5 periods were consecutive; at the end of each period the patients underwent a 24 hours Holter monitoring. The absence of significant VPBs/hour changes during the run-in period and the 3 placebo periods (522 ± 168, 461 ± 182, 547 ± 180 respectively) confirmed the stability of the arrhythmia during the whole study. Compared to placebo, SM and LD reduced VPBs/hour to 353 ± 194 (p 70% was observed in 67% and 33% of cases with SM and LD, respectively. SM and LD also induced a reduction of couplets/24 hours from 127 ± 59 to 21 ± 11 (p