Major
citalopram × Haloperidol
SSRI (selective serotonin reuptake inhibitor)×First-generation antipsychotics. Butyrophenone derivatives
Mechanism
Additive QT prolongation. Haloperidol is one of the strongest QT prolongers among typical antipsychotics, especially parenterally. Citalopram does so dose-dependently.
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
Avoid the combination, especially IV haloperidol. Alternative antipsychotics with minimal QT effect: olanzapine or aripiprazole. Alternative antidepressants: mirtazapine or agomelatine.