Major
citalopram × Escitalopram
SSRI (selective serotonin reuptake inhibitor)×Selective serotonin reuptake inhibitors (SSRIs)
Mechanism
Escitalopram is the S-enantiomer of citalopram. Combined use is a doubling of the same drug without therapeutic purpose. Additive QT prolongation and serotonin syndrome risk.
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
The combination is not prescribed. Choose one: escitalopram (more selective and active) is preferable. When switching, allow a 1-week washout.