SPARFLOXACIN BUT NOT LEVOFLOXACIN OR OFLOXACIN PROLONGS CARDIAC REPOLARIZATION IN RABBIT PURKINJE-FIBERS

Sparfloxacin, a fluoroquinolone antibacterial, has been reported to pr olong cardiac repolarization in some patients. In this study, we have investigated the in vitro cardiac electrophysiological effects of two other fluoroquinolones, levofloxacin and ofloxacin, and compared them with those exerted by sparfloxacin. Cardiac action potentials have bee n recorded from rabbit Purkinje fibers using conventional glass microe lectrodes. The influence of a sudden decrease in stimulation rate on r epolarization is examined. It is found that ofloxacin and levofloxacin (1-100 mu M) do not alter the action potential parameters even at a c oncentration as high as 100 mu M. The stimulation rate is without effe ct on repolarization. On the contrary, sparfloxacin (1-100 mu M) lengt hens concentration-dependently the duration of action potential, this effect being significant from the concentration of 10 mu M. A non sign ificant decrease in maximal rate of rise of phase 0 depolarization was observed at the concentration of 100 mu M. Under low stimulation rate , the sparfloxacin-induced prolonging effect was magnified and early a fterdepolarizations occurred in one of seven fibers from the concentra tion of 30 mu M and in four other fibers at the concentration of 100 m u M. These results suggest that levofloxacin and ofloxacin had no effe ct on cardiac cellular electrophysiology whereas sparfloxacin exerts p ure class III electrophysiological effects, which can explain the prol ongation of QT interval observed clinically in some patients and might become arrhythmogenic in the presence of other predisposing factors. (C) 1998 Elsevier, Paris.