不整脈治療薬ＭｅｘｉｌｅｔｉｎのＰｈａｒｍａｃｏｋｉｎｅｔｉｃｓとＰｈａｒｍａｃｏｋｏｄｙｎａｍｉｃｓ １回経口投与法による検討

Abstract

Mexiletine is a new antiarrhythmic agent which resembles to lidocaine electrophysiologically and is available for oral use. We investigated pharmacokinetic parameters and clinical effects on ventricular premature contractions (VPCs) of a single dose of mexiletine in 27 patients with frequent VPCs. The maximum concentration (Cmax) and the area under the time-concentration curve (AUC) increased dose-dependently, and the time to the maximum concentration after oral administration was 3.0 hours. There were significant correlations between dosage (mg/kg) and Cmax (r=0.87, p<0.01) or AUC (r=0.91, p<0.01). The biological half life in the elimination phase was 12.6 hours. The percentage of twenty-four hour cumulative urinary excretion of unchanged mexiletine was 7.87%. We investigated the suppressive effects on VPCs in 10 patients, who showed more than 300 VPCs per hour before administration of the drug in Holter dynamic ECG. Mexiletine was effective in suppression of VPCs in 5 patients (50%), in whom the single dosage of mexiletine was more than 200 mg. The minimum effective plasma concentration derived from these 5 patients was 0.59, μg/ml. Serious untoward effects were not observed at all, and PR, QRS, or QTc interval remained unchanged after administration.In conclusion, oral use of mexiletine is effective and safe to suppress VPCs.