Effects of the fluoroquinolone antibacterial drug ciprofloxacin on ventricular repolarization in the halothane-anesthetized guinea pig

The fluoroquinolone antibiotic ciprofloxacin has been reported to block delayed rectifier k+ channels at much higher concentrations than those at which it exerts its bactericidal activity. in this study using the halothane-anesthetized guinea pig,we assessed whether ciprofloxacin has a proarrhythmic activity. ciprofloxacin at a clinically relevant dose of 3 mg/kg,i.v. did not affect any electrocardiographic parameters. at 10 mg/kg,it prolonged the qt interval and the duration of the monophasic action potential of the ventricle under sinus rhythm and constant ventricular pacing (n = 6). the extents of its effects on the ventricular repolarization phase were comparable to those of another fluoroquinolone antibiotic moxifloxacin at a clinically relevant dose of 3 mg/kg (n = 6). meanwhile,the pr interval and qrs width were also increased by ciprofloxacin at 10 mg/kg,suggesting that the drug inhibited cardiac k+ channels as well as na+ and ca2+ channels in vivo. these results suggest that ciprofloxacin exerted a multiion channel- blocking action in the heart within the supra-therapeutic dose range. therefore,careful observation may be necessary for patients with heart disease receiving a higher dose of ciprofloxacin in order to prevent the emergence of resistance. © 2013 the japanese pharmacological society.