Extents of the sparfloxacin (3 -10 mg / kg, i.v.)-induced QT interval prolongation under normokalemic and hypokalemic conditions were assessed in halothane-anesthetized beagle dogs (n = 5). The hypokalemic condition was induced by an oral administration of furosemide (200 mg / kg per day) for 3 days, which decreased the serum potassium concentration from 3.65 ± 0.13 to 2.35 ± 0.13 mM (P<0.05). However, the decrease of potassium concentration by itself did not affect the extent of the

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... n-induced QT interval prolongation. These results indicate that acute hypokalemia may not severely sensitize the in situ heart for drug-induced long QT syndrome as previously thought.