Pharmacological ß-adrenoceptor blockade can augment torsadogenic action of IKr inhibitor: Comparison of proarrhythmic effects of d-sotalol and dl-sotalol in the chronic atrioventricular block dogs.

ABSTRACT

Information is still limited whether ß-blockade may augment or attenuate the onset of torsade de pointes in patients with IKr inhibitor-induced labile repolarization process. We compared the proarrhythmic effects of d-sotalol with those of dl-sotalol using the chronic atrioventricular block dogs, since d- and l-isomers share a similar blocking action on IKr but ß-blocking activity resides only in l-isomer. dl-Sotalol (3 mg/kg, p.o.) induced torsade de pointes in 3 out of 4 animals, whereas d-sotalol (3 mg/kg, p.o.) induced it in only 1 out of 4 animals. Thus, ß-blockade can augment torsadogenic action of IKr inhibitor.