Major
citalopram × Fluconazole
SSRI (selective serotonin reuptake inhibitor)×Antifungals, triazole derivatives
Mechanism
Dual risk. Fluconazole blocks CYP2C19 (strongly) and CYP3A4 (moderately) and prolongs QT itself. Citalopram plasma levels rise, plus additive QT prolongation.
Symptoms
QT prolongation on ECG. Clinically: dizziness, syncope, palpitations. Severe cases progress to polymorphic ventricular tachycardia (torsades de pointes). Risk is higher with hypokalaemia, hypomagnesaemia, bradycardia, and ischaemic heart disease.
Management
Cap citalopram at 20 mg/day when combined. ECG before start and every 3 days during therapy. Alternative antifungals: echinocandins for systemic mycoses or terbinafine for dermatophytosis.