Torsades de Pointes induced by a combination of garenoxacin and disopyramide and other cytochrome P450, family 3, subfamily A polypeptide-4-influencing drugs during hypokalemia due to licorice.

We report an 82-year-old man who developed ventricular tachycardia and Torsades de Pointes (TdP) after oral administration of garenoxacin, a novel quinolone antibiotic agent that differs from the third-generation quinolones, for pneumonia. He had hypokalemia (K 2.3 mmol/L) induced by licorice and also had received disopyramide for arrhythmia, bicalutamide for prostate cancer, and silodosin for prostate hypertrophy. After taking him off all drugs and administering spironolactone supplemented with potassium, his low serum potassium level was ameliorated. Therefore, although garenoxacin reportedly causes fewer adverse reactions for cardiac rhythms than third-generation quinolone antibiotics, one must be cautious of the interference of other drugs during hypokalemia in order to prevent TdP.