Electrophysiologic effects of the levo- and dextrorotatory isomers of sotalol in isolated cardiac muscle and their in vivo pharmacokinetics.
Dl-sotalol is a specific beta-adrenergic blocking agent that markedly lengthens cardiac action potential duration. To determine whether d-sotalol, with little or no beta-blocking effect, also lengthens repolarization, standard microelectrode studies were used to determine the electrophysiologic properties of dl-sotalol and its stereoisomers in isolated rabbit and canine myocardial fibers. D- and l-sotalol produced concentration-dependent increases in action potential duration to 50% (APD50) and 90% (APD90) repolarization, respectively, and in the effective refractory period without changes in the maximal rate of rise of action potential. In rabbit sinoatrial node, d- and l-sotalol produced concentration-dependent increases in spontaneous sinus cycle length (29 and 35%, respectively) by lengthening the action potential duration (by 58 and 55%) without effect on phase 4 depolarization. At the highest concentration (27.2 micrograms/ml), d- and l-sotalol prolonged APD90 (by 38 and 54%, respectively, in Purkinje fibers and by 32 and 34% in ventricular muscle) and effective refractory period (by 49 and 49% in Purkinje fibers and 29 and 40% in ventricular muscle). The effects of the two isomers were not significantly different. At the middle concentration (2.7 micrograms/ml), d-sotalol, unlike l-sotalol, had no beta-adrenergic blocking effect, but the electrophysiologic effects of dl-, d- and l-sotalol were indistinguishable. The data indicate that d-sotalol is equipotent with l-sotalol in lengthening the action potential duration and effective refractory period in cardiac muscle, an action unrelated to adrenergic antagonism or pharmacokinetic differences between the stereoisomers.
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D016275:Atrial Function; D004285:Dogs; D005260:Female; D006321:Heart / Q000502:physiology*; D006325:Heart Atria / Q000378:metabolism; D006352:Heart Ventricles / Q000378:metabolism; D007536:Isomerism; D007700:Kinetics; D008297:Male; D009132:Muscles / Q000378:metabolism / Q000502:physiology*; D009200:Myocardial Contraction / Q000187:drug effects; D011690:Purkinje Fibers / Q000378:metabolism / Q000502:physiology; D011817:Rabbits; D012849:Sinoatrial Node / Q000502:physiology; D013015:Sotalol / Q000097:blood / Q000494:pharmacology*; D016276:Ventricular Function
D013015:Sotalol