Major
Amiodarone × Escitalopram
Class III antiarrhythmics (Vaughan Williams)×Selective serotonin reuptake inhibitors (SSRIs)
Mechanism
Escitalopram (SSRI) is a citalopram enantiomer with dose-dependent QT prolongation. The FDA Lexapro label caps escitalopram at 20 mg/day specifically because of QT risk. Effects add with amiodarone.
Symptoms
QT prolongation on ECG. Clinically: dizziness, syncope, palpitations. Severe cases progress to polymorphic ventricular tachycardia (torsades de pointes) with risk of ventricular fibrillation and sudden cardiac death. Risk is higher with hypokalaemia, hypomagnesaemia, bradycardia, and ischaemic heart disease.
Management
Avoid where possible. If escitalopram is needed, cap at 10 mg/day; ECG before start and at 2 weeks, with potassium and magnesium maintained. Alternative antidepressants with minimal QT effect: mirtazapine or agomelatine.