Effects of an antiarrhythmic drug A-2545 on canine ventricular arrhythmia models; comparison with mexiletine and flecainide.
We investigated effects of a new Na+ channel blocking antiarrhythmic drug, A-2545, N-3 (2,2,5,5-tetramethyl-3-pyrroline-3-carboxamido)-propyl-phthalimide-hydro chloride, on various canine ventricular automaticity arrhythmias induced by two-stage coronary ligation, digitalis and adrenaline, and compared them with those of mexiletine. A-2545 showed antiarrhythmic effects, significantly decreasing the arrhythmic ratio of 24-h and 48-h coronary ligation-, digitalis- and adrenaline-induced automaticity arrhythmias. The antiarrhythmic plasma concentrations (IC50) of A-2545, 2 mg kg(-1) 10 min(-1), i.v., for 24-h and 48-h coronary ligation-, digitalis- and adrenaline-induced arrhythmias were 1.8, 1.3, 5.8 and 3.7 microg ml(-1), respectively, and that calculated for oral A-2545 (25 mg kg(-1)) in 24-h coronary ligation-induced arrhythmia was 1.8 microg ml(-1). A-2545 is specifically potent in suppressing coronary ligation-induced arrhythmias, i.e., decreasing the arrhythmic ratio nearly to zero by oral administration, and among the intravenously given experiments A-2545 was effective at lower concentrations than other arrhythmia models; A-2545, 2 mg kg(-1) 10 min(-1), was equipotent to 5 mg kg(-1) 10 min(-1) mexiletine in suppressing 24-h coronary ligation-induced arrhythmia, indicating that A-2545 is more potent than mexiletine. In order to determine whether A-2545 has arrhythmogenic effects, we used programmed electrical stimulation (PES)-induced reentry arrhythmias in dogs with old myocardial infarction and compared effects of A-2545 and flecainide. A-2545, 2 and 5 mg kg(-1) 10 min(-1), significantly suppressed the PES-induced arrhythmias in all six dogs without aggravating them. These arrhythmias were not markedly suppressed by flecainide either with 1 or 3 mg kg(-1) 1O min(-1); moreover even in one out of six dogs aggravation of arrhythmia was noted after 1 mg kg(-1) 10 min(-1). In conclusion, A-2545 suppressed various canine ventricular arrhythmias, and the antiarrhythmic effect of A-2545 was more potent than that of mexiletine, and A-2545 did not show arrhythmogenic effects compared to flecainide.
Xue
Y X
YX
Department of Pharmacology, Yamanashi Medical University, Japan.
Arita
J
J
Aye
N N
NN
Hashimoto
K
K
D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001145:Arrhythmias, Cardiac / Q000139:chemically induced; D001794:Blood Pressure / Q000187:drug effects; D003331:Coronary Vessels / Q000601:surgery; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D004562:Electrocardiography; D005424:Flecainide / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D008801:Mexiletine / Q000494:pharmacology*; D008954:Models, Biological; D015394:Molecular Structure; D011758:Pyrroles / Q000097:blood / Q000494:pharmacology*
D000889:Anti-Arrhythmia Agents; D011758:Pyrroles; D008801:Mexiletine; D005424:Flecainide; C109568:A 2545