Effects of the Fluoroquinolone Antibacterial Drug Ciprofloxacin on Ventricular Repolarization in the Halothane-Anesthetized Guinea Pig

Abstract

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 multi-ion 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.