[Correlations between plasmatic concentrations and antiarrhythmic effect of bunaphtine (author's transl)]

Antiarrhythmic effect of Bunaphtine (1.5 mg/kg) (e.v. in 2 min) was studied in 35 patients with ectopic rhythms, both ventricular and supraventricular. Arrhythmia was checked by continuous electrocardiographic recording. Bunaphtinemia was determined by spectrophotometric method. Plasma concentration levels proved that Bunaphtine is cleared from the blood in two different stages: T1/2alpha = 0.5 min and T1/2beta = 84.7 min. Antiarrhythmic effect was observed in connection with the fast distribution phase and it was even more evident when plasma concentration fluctuated around 3-4 mg/l. Extrasystoles increased when Bunaphtine levels diminished. The minimum effective level showed fairly good individual differences. In three cases with congestive heart failure, hepatic and renal insufficiency the increase or the appearance of ventricular extrasystole was related to high Bunaphtinemia levels. Risk of toxicity seems to be related to the dose and the administration methods. Cardiac decompensation or hepatic and renal insufficiency determine more elevated and protracted Bunaphtinemia levels.