Effects of a long-acting antiarrhythmic agent--QX-572--on therapy resistant ventricular tachyarrhythmias.

N,N-bis (phenylcarbamoylmethyl) dimethylammonium chloride (QX-572) was given to I2 patients with ventricular tachyarrhythmias resistant to other antiarrhythmic drugs, especially lignocaine. Most patients had acute myocardial infarction. The drug was slowly infused intravenously (8 mg/kg during 30 minutes) and was found very potent with a fully developed effect after about 20 munutes. In 9 of the patients the antiar- rhythmic effect of a single infusion of QX-572 lasted more than i5 hours. A mild degree of tachycardia occurred in all patients during the infusion period. Blood pressure response was more unpredictable. In one patient there was a substantial increase in blood pressure after completion of the QX-572 infusion. A slight blood pressure increase after completed QX-572 infusion was observed also in some of the other patients. Slight circumoral paraesthesia was felt by all patients. Only minor side effects were found and they were considered of little clinical importance. There was no clear correlation between tachycardia and bloodpressure changes and the antiarrhythmic effect of the drug. Its effectiveness in therapy-resistant ventricular arrhythmias and its long duration of action with no important side effects at therapeutically effective dosage might make QX-572 a valuable antiarrhythmic drug.