The efficacy and safety of a new dosage regimen of intravenous
disopyramide in ventricular arrhythmias were evaluated in 10 patients. Each had at least four
premature ventricular contractions (PVCs)/min during a 30-min period before dosing. By the classification of Lown et al., grade III
arrhythmia was present in four patients, grade IVA in three patients, and grade IVB in three patients.
Disopyramide was injected intravenously as a bolus of 0.5 mg/kg over 5 min. Each patient received two to three additional boluses of same strength with 5-min intervals between each dosing during the first hour. Continuous
intravenous infusion was started with the first bolus and continued at a rate of 1 mg/kg/hr for 3 hr and at 0.4 mg/kg/hr for 15 hr. All patients had continuous Holter monitoring throughout the 18-hr treatment period and for 30 to 60 min before treatment. In eight patients the grade of
arrhythmia after
drug decreased and the frequency of PVCs fell by 70% to 100% (greater than 85% in six patients and less than 85% in two patients), and the response persisted during the continuous infusion. In two patients
PVC frequency increased. For the group as a whole,
PVC frequency decreased on the average by 68.4%. Therapeutic serum levels (greater than 2 micrograms/ml) were reached after the first or second bolus and were maintained during the continuous infusion period. There were no side effects necessitating termination of
disopyramide infusion. The dosage regimen of intravenous
disopyramide evaluated was effective in 60% of patients with ventricular
arrhythmia, induced no severe toxic effects, and rapidly achieved therapeutic serum levels that were maintained during continuous infusion.