title: BW A256C, a chemically novel class 1 antiarrhythmic agent. A comparison of in vitro and in vivo activity with other class 1 antiarrhythmic agents.
abstract: BW A256C (5(3)-amino-6-(2,3-dichlorophenyl)-2,3(2,5)-dihydro-3(5)-imino-2 -isopropyl-1,2,4-triazine) is a novel class 1 antiarrhythmic agent designed to combine the features of potency with reduced central nervous system penetration. BW A256C reduced the maximum rate of depolarization of guinea-pig ventricle and dog Purkinje fibres in vitro (EC50, 2.2 X 10(-6) M and 1.8 X 10(-6) M, respectively), being significantly more potent than quinidine, lidocaine, disopyramide and flecainide. BW A256C was also more potent than these agents at inhibiting aconitine-induced arrhythmias in anaesthetized rats; however, unlike these agents, BW A256C was devoid of hypotensive activity at antiarrhythmic doses. In anaesthetized dogs, intravenous administration of BW A256C (0.25-1 mg kg-1) caused a dose-dependent suppression of ventricular arrhythmias that occurred on reperfusion of an occluded coronary artery. In conscious dogs, intravenous infusion (total dose, 1.5 mg kg-1) or oral administration of BW A256C (1.25-5 mg kg-1) caused dose-dependent suppression of the ventricular ectopic activity that occurred following 20-24 h of permanent coronary artery ligation. In the conscious dog, BW A256C was approximately 7 times more potent and was also longer acting than flecainide. Administration of BW A256C was not associated with any evidence of peripheral or CNS toxicity. However, plasma levels 3-4 times greater than the antiarrhythmic levels were associated with a proarrhythmic activity.
mesh_terms: D000157:Aconitine / Q000494:pharmacology; D000200:Action Potentials / Q000187:drug effects; D000758:Anesthesia; D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000494:pharmacology*; D001145:Arrhythmias, Cardiac / Q000188:drug therapy / Q000209:etiology; D004285:Dogs; D004562:Electrocardiography; D005260:Female; D006168:Guinea Pigs; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors; D014227:Triazines / Q000494:pharmacology*
chemical_list: D000889:Anti-Arrhythmia Agents; D014227:Triazines; C049707:palatrigine; D000157:Aconitine