Fluconazole- and levofloxacin-induced torsades de pointes in an intensive care unit patient

Patients initiated on fluconazole and levofloxacin should be closely monitored for QTc-interval prolongation. While there have been published reports of fluconazole and levofloxacin causing QTc-interval prolongation when given alone, coadministration of these two agents may further increase this risk. This case describes an episode of TdP in which levofloxacin and fluconazole were likely significant factors. QT prolongation was present at baseline prior to drug initiation (QTc = 454-505 ms) and levofloxacin resulted in further prolongation (QTc = 480-536 ms). After two days of therapy with fluconazole, overlapping with levofloxacin, the patient had an episode of PMVT with syncope, and progressive QT prolongation was evident (QTc = 554 ms). Only mild hypokalemia (potassium concentration = 3.6 meq/L) was present, and not additional etiologies for TdP were identified. Levofloxacin and fluconazole were discontinued and no further PMVT was observed, but the QT interval did not return to normal until after an additional 11 days (QTc = 436 ms). As in many cases of TdP, multiple factors were involved. Renal failure, drug dosing, mild hypokalemia, and a baseline abnormal QT interval potentiated the role of levofloxacin and fluconazole in the development of TdP. We recommend that neither drug be used alone or in combination when there is baseline QT prolongation. We also recommend that concomitant use of these agents be avoided when possible. If combination therapy is required, caution is warranted, particularly in patients with risk factors for QT prolongation. Specific attention should be given to drug dosing, interactions, electrolytes, and ECG monitoring.