Comparison of intravenous mexiletine and lidocaine for the treatment of ventricular arrhythmias.

The efficacy and safety of intravenous loading of mexiletine was compared to lidocaine in patients with ventricular premature depolarizations (VPDs). Seventeen men and five women, average age 63 years, completed this randomized parallel study. Twelve patients recelved mexiletine intravenously at (5 to 10 mg/min) until ≥95% VPD suppression was achieved or a total of 450 mg of drug was given. The average loading dose of mexiletine was 4.4 mg/kg, at an infusion rate of 0.1 mg/kg/min. Ten patients received lidocaine (1 mg/kg) given over 3 minutes, with a second similar bolus given if after 10 minutes ≥95% VPD suppression was not achieved. Total VPDs were determined for the 60 minutes before drug administration, during drug infusion, and 60 minutes thereafter. Eleven of 12 (92%) patients receiving mexiletine were full responders (≥95% suppression) and one was a partial responder (≥75% ≤95% suppression). Five of 10 lidocaine patients (50%) were full responders, three (30%) were partial responders, and two failed to respond. At peak suppression, mexiletine reduced mean VPD from 37 ± 335 minutes (mean ± S.D.) to 0.8 ± 0.95 minutes (p < 0.01) and lidocaine decreased mean VPDs from 28 ± 475 minutes to 4.7 ± 2.25 minutes (p < 0.01). Mexiletine resulted in greater suppression of VPDs than lidocaine in terma of mean percent reduction (96% vs 68%, p < 0.01). All lidocaine patients had therapeutic plasma levels (range 1.6 to 3.5 μg/ml). In the mexiletine patients, there was one subtherapeutic and one toxic level observed (mean 1.4 μg/ml, range 0.4 to 3.2 μg/ml). No significant changes in blood pressure, heart rate, or ECG intervals were noted for either drug. Three mexiletine and one lidocaine patient experienced transient adverse effects. Intravenous mexiletine was found safe and effective and may be a useful alternative drug in the management of ventricular arrhythmias.