Two groups of unanesthetized dogs, each consisting of six animals with
ventricular tachycardia caused by two-stage
ligation of the anterior descending branch of the left coronary artery on the day before treatment, were given continuous
intravenous infusions of 0.5 mg/kg/min of either
droxicainide [DL-N-(2-hydroxyethyl) pipecolinyl-2,6-dimethylanilide] hydrochloride or
lidocaine hydrochloride until convulsions occurred. At low cumulative doses of either
drug, the infusions produced a progressive reduction in the frequency of
ventricular ectopic beats, but no significant changes in the sinus rate, the PR or QRS intervals of normal sinus beats, the arterial and central venous pressures, or the respiratory rate. At higher cumulative doses
lidocaine produced sedation, and both drugs produced
emesis and then convulsions that subsided soon after termination of treatment. With respect to both the cumulative doses and plasma concentrations at which they reduced the frequency of ectopic beats by 25, 50, and 75% and at which they produced convulsions,
droxicainide was a more potent antiarrhythmic agent than
lidocaine and had a wider margin of safety.