RESUMEN
<p><b>AIM</b>To learn the electrophysiological interference of levofloxacin (LVFX) to heart in guinea pig.</p><p><b>METHODS</b>High, moderate and low doses of LVFX were given to the anesthetic guinea pig via i.p., and QT interval span and corrected QT-interval span in the II leading lines of ECG were recorded and analyzed from 5 min to 360 min after the drug administration. Single ventricular myocytes were obtained and impacted by LVFX solution of different concentrations. Then delayed rectifier potassium currents (I(K)) on single cells were recorded with whole-cell patch clamp technique, and compared with control group(without impact of LVFX).</p><p><b>RESULTS</b>(1) After the administration of LVFX, at the dose of 200 mg/kg. QT-interval span was significantly elongated, and the increasing rate is 19.38% +/- 3.15% (P < 0.05). While at the relatively lower doses of 50 mg/kg and 100 mg/kg, the elongation is of low/no significance (P > 0.05). (2) LVFX inhibited I(K) dose-dependently and time-dependently.</p><p><b>CONCLUSION</b>LVFX might prolong the QT-interval span by the mechanism of inhibiting I(K), which implies a potential risk in clinical application.</p>