QTc-prolongation during ciprofloxacin and fluconazole combination therapy: prevalence and associated risk factors

Abstract

Aim (s)

Ciprofloxacin and fluconazole combination therapy is frequently used as prophylaxis for and treatment of infections in patients with haematological malignancies. However, both drugs are known to prolong the QTc-interval, which is a serious risk factor for Torsade de Pointes (TdP). Therefore, the aim of this study was to assess the prevalence of QTc-prolongation during ciprofloxacin and fluconazole use. The secondary objective was to determine associated risk factors of QTc-prolongation in these patients.

Methods

A prospective observational study was performed in patients admitted to the Erasmus University Medical Centre and treated with ciprofloxacin and fluconazole. A twelve-lead electrocardiogram (ECG) was recorded at the T_max of the lastly added drug. Main outcome was the proportion of patients with QTc-prolongation during treatment. The following potential risk factors were collected: patient characteristics, serum electrolyte levels, dosage of ciprofloxacin and fluconazole, renal and liver function and concomitant use of other QTc-prolonging drugs and CYP3A4-inhibitors.

Results

170 patients were included, of which 149 (87.6%) were treated for haematological malignancies. The prevalence of QTc-prolongation was 4.7%. No risk factors were found to be associated with QTc-prolongation. The QTc-interval increased with 10.7 ms (95% confidence interval (CI) 7.2 – 14.1 ms) during ciprofloxacin – fluconazole therapy.

Conclusion

The prevalence of QTc-prolongation in patients using ciprofloxacin and fluconazole is low compared to the prevalence in the general population which is varying from 5 – 11%. Also, no risk factors were found. Given the low prevalence, routine ECG monitoring in patients on this therapy should be reconsidered.

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