Procainamide absorption studies to test the feasibility of using a sustained-release preparation

Using in vitro techniques it was confirmed that whilst the release of procainamide from the conventional formulation (Pronestyl) was rapid, that from the sustained-release preparation (Cardiorytmin Retard) occurred over a prolonged period. 2 The peak plasma procainamide concentrations after single doses of Cardiorytmin Retard were relatively lower and occurred later than those after single doses of Pronestyl. Furthermore, after reaching a peak, the fall in plasma procainamide concentration was less rapid after the sustained-release preparation. Early urinary recovery of procainamide in patients and in healthy volunteers was greater after Pronestyl than after Cardiorytmin Retard, though overall recovery in urine was similar. These findings indicate that the absorption of the sustained-release preparation is slower, though the overall bioavailabilities of the two preparations are almost the same. 3 These results confirm the feasibility of using a sustained-release procainamide preparation, such as Cardiorytmin Retard, since it would be possible to administer the same amount of drug in fewer daily doses without plasma concentrations becoming ineffective towards the end of each dosing interval.

Effect of procainamide and lidocaine on total electrical systole of ventricular premature depolarizations

The effect of lidocaine and procainamide on the electrocardiogram of a patient with coupled ventricular premature depolarizations was observed after continuous electrocardiographic monitoring during a control period and drug therapy. First lidocaine, 100 mug/kg/min, and 3 1/2 hours later procainamide, 200 mug/kg/min, were infused until the arrhythmia was completely suppressed. In each drug study, blood samples were taken every 5 minutes for determining plasma drug concentration. In addition to important differences between the two drugs on the standard electrocardiographic intervals, a new electrocardiographic phenomenon was recognized: a change in the total electrical systole of the ventricular premature depolarization (ventricular premature depolarization-Q-T interval). These observations are discussed and related to the electrophysiologic properties reported for each of these agents.

Comparison of procainamide and mexiletine in prevention of ventricular arrhythmias after acute myocardial infarction

The incidence of ventricular arrhythmias after myocardial infarction has been compared in a controlled study of procainamide, mexiletine, and placebo. Sixty male patients who has sustained a myocardial infarction and had received lignocaine for ventricular tachycardia or ventricular ectopic beats which were R-on-T, multiform, or close-coupled took part. The efficacy of the drugs was evaluated by continuous 24-hour recordings of the electrocardiogram on the 4th and 10th days after admission to the study. Procainamide was given as 500 mg. 4-hourly and mexiletine as 250 mg. 8-hourly with corresponding placebo regimens for 12 days. 77% of patients receiving placebo showed serious ventricular rhythm disorders compared with 33% receiving antiarrhythmic therapy (p smaller than 0.05). Although only 35% of patients receiving procainamide achieved accepted therapeutic plasma concentrations compared with 95% of those receiving mexiletine, both drugs were equally effective antiarrhythmically. The only major adverse effect of therapy noted was development of a positive antinuclear factor in a procainamide-treated patient. These results demonstrate the efficacy of oral antiarrhythmic agents in the management of ventricular arrhythmias after acute myocardial infarction. Mexiletine has the advantage of less frequent administration and lower toxicity.

Control of arrhythmias following ligation of the circumflex artery

In experimental work, three groups of 10 dogs each were subjected to ligation of the circumflex coronary artery. One group was given prophylactic medication with procainamide and another group was allowed a 2 hour interval between thoracotomy and ligation. The effects of these measures on the incidence of ventricular arrhythmias during the 30 minutes immediately after coronary artery occlusion were then compared. The two groups of animals on which these preventive measures were tested both showed a significant reduction in incidence of arrhythmias as compared to the control group. The therapeutic use of procainamide was also assessed by administering the drug intravenously to all animals developing postligation arrhythmias in the two groups which were not prophylactically medicated. In 46 per cent of these cases, the arrhythmias were suppressed and threatened ventricular fibrillation was obviated.

Programmed "trendscription." A new approach to electrocardiographic monitoring

A new approach to monitoring of episodic but frequently recurring arrhythmias has been developed, consisting of condensation of electrocardiographic information on a special drum recorder, a programmer that permits selection of intervals and durations for monitoring, and a telemetry unit for transmission of the electrocardiographic signal. We used this system to manage three selected cases.

Elimination rate of N-acetylprocainamide after a single intravenous dose of procainamide hydrochloride in man

Equations were derived which made it possible to determine the elimination rate of N-acetylprocainamide from urinary data after intravenous administration of procainamide hydrochloride. A single dose of 500 mg of the drug was infused intravenously in four healthy subjects. On the basis of theose equations, the formation rate of the metabolite could be calculated presuming that all rate processes were occurring by first-order processes. However, close examination of the excretion rate data appears to support the contention that the formation or excretion of N-acetylprocainamide may be occurring by a saturable process

Pharmacologic and clinical control of antiarrhythmic drugs

Knowledge of pharmacokinetics and pharmacodynamics is a powerful tool for controlling cardiac arrhythmias with drugs even though antiarrhythmic drugs are potentially quite toxic. If the diagnosis and drug selection are correct at the outset of therapy, the clinician can use his knowledge of pharmacokinetics to achieve arrhythmia control with a minimum of personal effort and risk to his patient.

Pharmacokinetics of procainamide intravenously and orally as conventional and slow-release tablets

Pharmacokinetics of procainamide were studied in healthy volunteers after single doses intravenously and orally as conventional and slow-release tablets and after repeated oral doses to steady state. The initial distribution after intravenous administration was rapid and the overall elimination in the beta-phase corresponded to t1/2 of 2.7 hr. The mean volume of the central compartment was small and only 4 percent of V-d (beta), which was 2.3 l/kg body weight. About 65 percent was excreted unchanged after intravenous administration and about 55 percent after a single oral dose of 500 mg. The recovery of the metabolite N-acetylprocainamide was 12 percent after both routes of administration. Procainamide was completely absorbed from the gastrointestinal tract and the first-pass elimination was very limited. The rates of absorption from the tablet compositions were well correlated to the in vitro dissolution properties. Administration of slow-release tablets every 8 hr gave about the same mean plasma level at steady state as ordinary tablets given every 4 hr, and the availability was the same from both preparations. The occasional high plasma concentration peaks after ordinary tablets were not observed after the slow-release tablets. Renal clearance was about 500 ml/min, indicating an active secretion in the tubules.

Sustained accelerated idioventricular rhythm

A 73-year-old white man became easily fatigued and hypotensive six weeks after a documented acute inferior myocardial infarction. Continuous ECG monitoring showed a sustained tachycardia with a right bundle branch block pattern. A His bundle electrogram showed no His deflection prior to ventricular activation. The patient was successfully treated with intravenous procaine amide resulting in reversion to sinus rhythm, loss of symptoms, and return of blood pressure to normal levels. The unique aspects of this case and therapeutic considerations in the management of this problem are discussed.