Pharmacokinetic and pharmacodynamic studies of procainamide given intermittently intravenously in patients with severe ventricular arrhytmias.

In 15 patients with coronary heart disease and ventricular arrhythmias 100 mg of procainamide was given intravenously every 5 min until arrhythmia was abolished, or the patient received 1000 mg of the drug, or side-effects appeared. Then patients were placed on oral maintenance therapy 3 or 4 g daily according to their weight. In 13 out of 15 patients arrhythmia was completely suppressed after intravenous injections of the drug. Plasma procainamide concentrations, including N-acetylprocainamide levels in some patients, were monitored and a therapeutic range of 6.3--10.3 microgram/ml for intravenous therapy was found. ECG intervals changes, slowing of heart rate and decrease in systolic and diastolic blood pressure were seen but no serious side-effects were observed. The significance of monitoring plasma drug concentrations, including levels of N-acetylprocainamide during prolonged maintenance therapy, have been discussed.