The Antiarrhythmic Activity of Meobentine Sulfate in Man

Meobentine (sulfate) has antifibrillatory and antiarrhythmic activity in canine models. The antiarrhythmic, pharmacokinetic, and adrenergic neuronal blocking effects of meobentine were assessed in 15 patients with chronic, high-frequency ventricular ectopic depolarizations (VEDs). Eleven of the 15 patients had recurrent nonsustained ventricular tachycardia. The patients were given a series of gradually increasing single doses of meobentine; six received oral meobentine and nine had infusions. The antiarrhythmic efficacy of meobentine was assessed by a comparison of arrhythmia frequency during placebo given on days just prior to meobentine. Oral therapy with meobentine at dosages above 20 mg/kg caused diarrhea, and well-tolerated dosages achieved peak concentrations of 0.69 micrograms/ml (range 0.5-1.0 micrograms/ml). Antiarrhythmic activity was seen in only one patient with oral meobentine. In contrast, intravenous infusions (6.75-34.2 mg/kg) achieved concentrations ranging from 1.3-9.8 micrograms/ml. There was a linear relationship between pseudo-steady-state plasma concentrations and dosage, r = 0.82, p less than 0.01. Antiarrhythmic activity was seen in four of nine patients who received intravenous meobentine over a range of concentrations from 2.5-4.5 micrograms/ml. Four patients developed evidence of adrenergic neuronal blockage (loss of the venous reflex response); two at dosages of 16.2 mg/kg, one at 24.3 mg/kg, and one at 34.2 mg/kg. In one individual (24.3 mg/kg), the adrenergic neuronal blockade was associated with an acute episode of shortness of breath, orthopnea, and cough. With intravenous meobentine, there was a linear relationship between dosage and AUC, and the elimination half-life ranged from 11-27 h.(ABSTRACT TRUNCATED AT 250 WORDS)