Escitalopram × Fluconazole

Fluconazole prolongs QT by directly blocking the Ikr potassium current, in the words of its SmPC, which also contraindicates QT-prolonging drugs metabolised through CYP3A4. The escitalopram SmPC contraindicates any QT-prolonging drug alongside it: the ban is written broadly, and the classes in brackets are examples. Kinetics adds a second layer: fluconazole inhibits CYP2C19, the main metabolic path for escitalopram, so antidepressant levels rise along with its dose-dependent QT effect.

QTc prolongation on ECG, palpitations, dizziness, syncope. The end point is polymorphic ventricular tachycardia of the torsade type progressing to ventricular fibrillation. The risk is higher with hypokalaemia, hypomagnesaemia, bradycardia, decompensated heart failure and in women.

The pair sits in the escitalopram SmPC contraindications, so the question is which drug stays, not how far to cut the dose. In superficial mycoses topical forms give almost no systemic absorption and the question disappears. In systemic mycosis an echinocandin is chosen. Switching to another azole does not lift the contraindication: the fluconazole SmPC links QT prolongation to other azoles as well. If the pair continues, potassium, magnesium and QTc stay under watch.