Drug interactions between fluconazole and Levaquin

MONITOR: In one case report, coadministration of fluconazole and levofloxacin was suspected in causing QT prolongation and torsade de pointes ventricular arrhythmia. The exact mechanism of interaction is unknown, although both agents have individually been associated with these events on rare occasions. The case patient was a 53-year-old man who was being managed for possible nosocomial pneumonia and received intravenous levofloxacin for 8 doses over 14 days and intravenous fluconazole for 2 doses over 2 days before developing torsade de pointes. His QTc interval was 655 ms and remained prolonged for 12 days after resolution of the arrhythmia, despite discontinuation of both medications and substitution with caspofungin. His medical history includes paroxysmal atrial fibrillation, chronic obstructive pulmonary disease, type I diabetes mellitus, and hemodialysis-dependent diabetic nephropathy. Electrolyte imbalance and prior medications were ruled out as possible causes. However, the patient may have received more fluconazole than intended due to inadvertent administration on a day he did not receive dialysis.

MANAGEMENT: Caution is advised if fluconazole is coadministered with levofloxacin. Patients should be advised to seek medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, palpitations, or syncope.