QT-prolonging class I drug, disopyramide, does not aggravate but suppresses adrenaline-induced arrhythmias. Comparison with cibenzoline and pilsicainide

Assessment of drug-induced proarrhythmias due to pilsicainide in patients with atrial tachyarrhythmias

Background

Pilsicainide, a pure Na⁺ channel blocker, is a popular antiarrhythmic drug for the management of atrial tachyarrhythmias (AT), in Japan. However, serious drug-induced proarrhythmias (DIPs) may unexpectedly occur. We assessed the clinical background of AT patients presenting with DIPs caused by pilsicainide.

Methods

This study retrospectively enrolled 874 consecutive patients (543 men, 63.6±15.3 years old, and 57.9±16.5 kg of body weight), who were orally administered pilsicainide for AT management. We evaluated the relationship between DIPs and serum pilsicainide concentration, renal dysfunction (estimate glomerular filtration rate, eGFR), and electrocardiogram (ECG) parameters.

Results

Among the patients, 154 (17.6%) had renal dysfunction (eGFR<50 mL/min), including 12 (1.4%) on hemodialysis. DIPs were present in 10 patients (1.1%): all had renal dysfunction, and one was on hemodialysis. The eGFR in DIP patients was significantly lower than that in the non-DIP patients (32.2±15.1 vs. 68.4±22.1 mL/min, p<0.001). Among the clinical factors measured, only renal dysfunction (eGFR<50 mL/min) was significantly associated with DIPs (OR 44.6; 95% CI 5.61–335.0, p<0.001). Interestingly, among the ECG parameters, the corrected QT (QTc) intervals in DIP patients were longer than those in non-DIP patients (555.8±37.6 vs. 430.7±32.6 ms, p<0.001). As pilsicainide concentration increased, both QRS and QTc intervals prolonged. The latter were improved by discontinuing pilsicainide administration, and additional treatments.

Conclusions

DIPs caused by pilsicainide administration were strongly associated with renal dysfunction. Hence, confirmation of renal function would be necessary prior to and/or during the pilsicainide administration.

An open-label, single-dose, parallel-group, dose-increasing study comparing the pharmacokinetics and tolerability of pilsicainide hydrochloride in healthy Korean and Japanese male subjects

BACKGROUND

Pilsicainide hydrochloride is a class IC antiarrhythmic agent used for the treatment of supraventricular and ventricular arrhythmias.

OBJECTIVE

The objective of this study was to compare the pharmacokinetics and tolerability of pilsicainide in healthy Korean and Japanese male volunteers to satisfy regulatory requirements for marketing pilsicainide in the Republic of Korea.

METHODS

This was an open-label, single-dose, parallel-group, dose-increasing study. It was simultaneously conducted in healthy Korean and Japanese volunteers from September 2005 through May 2006; pilsicainide was approved for use in the Republic of Korea in 2007. Subjects for the 100-mg group were enrolled after the performance of tolerability evaluations in the 50-mg dose group. Serial blood and urine samples were collected up to 24 hours after dosing, and drug concentrations in plasma and urine were determined by high-performance liquid chromatography. Tolerability was evaluated by monitoring adverse events (AEs), clinical laboratory parameters, and results of 12-lead electrocardiograms (ECGs).

RESULTS

Sixteen healthy Korean male subjects (mean [SD] age, 24.5 [4.2] years; weight, 71.8 [5.5] kg; height, 176.6 [6.3] cm) and 16 healthy male Japanese subjects (age, 24.7 [4.9] years; weight, 60.2 [4.4] kg; height, 171.9 [6.4] cm) were enrolled in the study. Values for AUC and C(max) of pilsicainide increased proportionally with dose escalation in all subjects. Pilsicainide reached C(max) 0.5 to 1.5 hours after dosing in both the Korean and Japanese subjects. The mean (SD) dose-normalized values for C(max) for the Korean and Japanese subjects were 9.4 (1.9) and 9.2 (1.6) ng/mL/mg, respectively. The mean (SD) dose-normalized values for AUC(0-infinity) were 56.0 (8.0) ng . h/mL/mg in the Korean subjects and 53.8 (8.1) ng . h/mL/mg in the Japanese subjects. None of these findings were statistically significant. A total of 9 AEs occurred in 7 of the 16 Korean subjects; they included dizziness, feeling of being hot, somnolence, and atrioventricular block. All of the AEs were mild in severity and were considered possibly related to pilsicainide. Two of the 16 Japanese subjects had a total of 4 AEs. All of the AEs occurred in the subjects treated with 50 mg. Of the 2 subjects with AEs, 1 subject had a decrease in blood pressure, a sense of discomfort, and PR-interval prolongation on ECG, while the other developed a premature ventricular contraction (PVC). The PR-interval prolongation and PVC were determined to be possibly related to pilsicainide, and these were mild in severity. The other AEs (ie, decreased blood pressure, sense of discomfort) were moderate in severity.

CONCLUSIONS

The results of this study suggest that the pharmacokinetic profile of pilsicainide was not significantly different between these healthy Korean and Japanese male volunteers. A single dose (50 or 100 mg) of pilsicainide was well tolerated in both ethnic groups.

Arrhythmia Models for Drug Research: Classification of Antiarrhythmic Drugs

The aim of this study was to classify antiarrhythmic drugs based on their effectiveness on 6 in vivo arrhythmia models, mainly using dogs. The models were produced by two-stage coronary ligation, digitalis, halothane-adrenaline, programmed electrical stimulation in old myocardial infarction dogs, coronary artery occlusion/reperfusion, or chronic atrioventricular block. Na(+)-channel-blocking drugs suppressed two-stage coronary ligation and digitalis arrhythmias. Ca(2+)-channel blockers and beta-blockers suppressed halothane-adrenaline arrhythmia. Positive inotropic drugs aggravated halothane-adrenaline arrhythmia, but did not aggravate digitalis arrhythmia. K(+)-channel blockers suppressed programmed electrical stimulation induced arrhythmia, but induced torsades de pointes type arrhythmia in chronic atrioventricular block dogs and aggravated halothane-adrenaline arrhythmia. Na(+)/H(+)-exchange blockers suppressed coronary artery occlusion/reperfusion arrhythmias. This classification may be useful for predicting the clinical effectiveness in the preclinical stage of drug development.

Slowing Na+ channel inactivation prolongs QT interval and aggravates adrenaline-induced arrhythmias

We investigated the effects of prolonged repolarization induced by slowed inactivation of Na+ channel on adrenaline-induced arrhythmias in halothane anesthetized, closed-chest dogs. We used sea anemone toxins (ATX-II and Anthopleurin-A) to prolong ventricular repolarization and examined their effects on adrenaline arrhythmias. Sea anemone toxins prolonged the QTc- and JTc-intervals (P<0.01), but did not affect the PQ interval, QRS duration, heart rate and mean blood pressure. Although sea anemone toxins did not induce any arrhythmias by themselves, under the treatment with these toxins, arrhythmias were induced by non-arrhythmia-inducing doses of adrenaline in four dogs out of seven and the control arrhythmias induced by adrenaline were aggravated. These results indicate that, similar to the inhibition of K+ channels by class III drugs, which we have already reported, slowing Na+ channel inactivation with QTc prolongation also aggravates adrenaline-induced arrhythmias.